Hi there. Thank you for your mod. Unfortunately, there is an incompatibility with Cosmos portals and its library . Indeed, when I remove your library architectury-1.29.50.jar the client doesn't back to the version menu (it just says that the library architectury-1.29.50.jar is missing) so I guess there is a conflict in your file with Cosmos Portals mod/library.

Here is a fresh launcher log = https://pastebin.com/raw/ycx1mJeL and a screenshot of the bug = https://ibb.co/HFVDDzf .

Thank you for your time.

Sorry, I haven't use the correct version of the library ! All good, everything is working fine.