As the old config can not be read with the newer sponge builds there is no automatic way to delete them. However you could try something like /kill @e[type=armor_stand]. Please be careful, make a backup before you execute that command. It kills all armorstands in the current world you are in.
Edit: Or /kill @e[type=ArmorStand], depends on your minecraft version.
It seems as though all of my holograms disappeared after a restart. They are still in the configs but they are not visible on the map. I have tried reloading the plugin and that did not work either. I am on version 2.0 and I am using sponge: spongeforge-1.10.2-2171-5.1.0-BETA-1976.jar
I canāt reproduce your described behavior with a fresh setup of your mentioned version. Could you please also try it without any other mods/plugins?
Sure, I will set up a new test server tonight and get back to you.
So it works on a fresh server, but Iām not sure what would be conflicting with it on my main server. It wipes ALL the holograms after every restart.
Please send a list if all your plugins/mods and I can try to guess which one might cause it. But thatās very vague. Of course it is better when you start with a fresh server and then add one mod/plugin at a time and test if the holograms dissapear.
Edit: Do you see armorstand in spectator mode? Maybe only the text dissapears.
Using Spectator mode I still canāt see them, here is a list of plugins I am using:
EMPSponge
GriefPrevention (I think it may be this, but I canāt think of what flag would be stopping armorstands. I tried to allow the spawning of armorstands entities and reloaded the holograms but still nothing.)
LuckPerms
Nucleus
EasyScoreboards
WorldEdit
I canāt think of a plugin that would do that but grief prevention seems to be the most likely one.
You have to create the hologram everytime it is gone because the armorstand is simply an entity that is saved with the world. The armorstands are not spawned everytime when the plugin reloads, they only get the text updated if they can still be found.
Start with a fresh server:
Okie, I finally got it fixed. I had overlooked a flag that was blocking it from spawning, but itās all good now. Thank you so much for your help!
I seem to be getting this error whenever I try to make a hologram of any sort. Any Help?
[Sponge]: Error occurred while executing command 'holograms create Welcome to Serious Servers' for source EntityPlayerMP['curscascis'/4884, l='world', x=29511.64, y=80.26, z=30092.14]: org.spongepowered.api.world.World.createEntity(Lorg/spongepowered/api/entity/EntityType;Lcom/flowpowered/math/vector/Vector3d;)Ljava/util/Optional;
java.lang.NoSuchMethodError: org.spongepowered.api.world.World.createEntity(Lorg/spongepowered/api/entity/EntityType;Lcom/flowpowered/math/vector/Vector3d;)Ljava/util/Optional;
at de.randombyte.holograms.Hologram$Companion.spawn(Hologram.kt:24) ~[Hologram$Companion.class:?]
at de.randombyte.holograms.commands.SpawnTextHologramCommand.executedWithPermission(SpawnTextHologramCommand.kt:16) ~[SpawnTextHologramCommand.class:?]
at de.randombyte.holograms.commands.PermissionNeededCommandExecutor.executedByPlayer(PermissionNeededCommandExecutor.kt:12) ~[PermissionNeededCommandExecutor.class:?]
at de.randombyte.holograms.commands.PlayerCommandExecutor.execute(PlayerCommandExecutor.kt:17) ~[PlayerCommandExecutor.class:?]
at org.spongepowered.api.command.args.ChildCommandElementExecutor.execute(ChildCommandElementExecutor.java:179) ~[ChildCommandElementExecutor.class:1.10.2-2171-5.1.0-BETA-2005]
at org.spongepowered.api.command.spec.CommandSpec.process(CommandSpec.java:351) ~[CommandSpec.class:1.10.2-2171-5.1.0-BETA-2005]
at org.spongepowered.api.command.dispatcher.SimpleDispatcher.process(SimpleDispatcher.java:333) ~[SimpleDispatcher.class:1.10.2-2171-5.1.0-BETA-2005]
at org.spongepowered.common.command.SpongeCommandManager.process(SpongeCommandManager.java:291) [SpongeCommandManager.class:1.10.2-2171-5.1.0-BETA-2005]
at net.minecraft.command.ServerCommandManager.func_71556_a(SourceFile:83) [bd.class:?]
at net.minecraft.network.NetHandlerPlayServer.func_147361_d(NetHandlerPlayServer.java:913) [me.class:?]
at net.minecraft.network.NetHandlerPlayServer.func_147354_a(NetHandlerPlayServer.java:892) [me.class:?]
at net.minecraft.network.play.client.CPacketChatMessage.func_148833_a(SourceFile:37) [im.class:?]
at net.minecraft.network.play.client.CPacketChatMessage.func_148833_a(SourceFile:9) [im.class:?]
at org.spongepowered.common.network.PacketUtil.onProcessPacket(PacketUtil.java:136) [PacketUtil.class:1.10.2-2171-5.1.0-BETA-2005]
at net.minecraft.network.PacketThreadUtil$1.redirect$onProcessPacket$zjd000(SourceFile:39) [fl$1.class:?]
at net.minecraft.network.PacketThreadUtil$1.run(SourceFile:13) [fl$1.class:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_45-internal]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_45-internal]
at net.minecraft.util.Util.func_181617_a(SourceFile:45) [h.class:?]
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:668) [MinecraftServer.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:387) [ld.class:?]
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:613) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:471) [MinecraftServer.class:?]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_45-internal]Please use version 2.0 for api 5.1.0.
Thanks I realized I downloaded from the wrong place.
@RandomByte So I manually removed a multiline hologram and itās still in-game. What MC command to I do to remove the nearest entity or whatever I have to do?
Execute /holograms force-delete, as it says in the first post. It removes every ArmorStand in a radius of 2 blocks.
Alright thanks, somehow I completely overlooked that.
Hello,I like this plugin very much.I want to share this plugin in MCBBS.Can you agree with me?
www.mcbbs.net 
Yes
What if someone has an issue with my plugin? The best thing would be that they report it either here or on GitHub. And does the post in your forum get updated when I change it here?
Note: the screenshot you posted is not reproducible with this plugin, itās like false advertisement.
Is there a link to this forum? That would be great! 
I have a problem. I removed the pluggin while I decided to world edit my spawn into a new world, it copied the holograms and they are not classed as holograms for some reason and they are stuck there permanently (even without the pluggin!). Lucky they can stay perm if it canāt be fixed. but I would like this fixed D: