When I add Origin++ mod, I can't choose origin or sometimes I get a connection lost error when creating world. I had encountered this problem in previous versions and it was solved by downloading a mod. But I forgot the name of that mod.

Try installing XL Packets Fabric and/or Connectivity

Can you attach a log?

latest.log
rei.log
rei-issues.log
When I add the origin plus mod, it causes me to enter without choosing an origin when creating the world.

problem fixed.

Do you have any other mods whatsoever, you need origins for this to work. Otherwise IDK

yes there are other mods and there is origin mod