I tried adding sponge and it wouldn’t start. It works perfectly fine with only forge.
Please go to your logs folder and upload the debug.log file to one of these sites, and then give us the link. Please make sure its the log file from when you tried to install Sponge.
https://paste.gg
https://paste.feed-the-beast.com
Secondarily when asking for help, please explain the issue more. Is it crashing? Is it just not starting? Is it starting but sponge isn’t loaded? What mods do you have? What version of Sponge are you using? Etc.