Hello,
CCA is now enforcing this mod to be installed on all clients. Vanilla players are unable to join due to https://ladysnake.org/wiki/cardinal-components-api/upgrade-instructions/CCA-6-changes#client-optional-components

Here is an example of what happens(with a different mod, but the error message is the same) with a solution to enable vanilla clients to join again.
Ladysnake/Cardinal-Components-API#174

Thank you

Ah, lovely, I completely missed that they changed that. I'll find a workaround soon™.

Thank you.
My friends and I really like this mod, thank you for developing it and sharing it with all of us. ❤️

Should be fixed as of version 1.10.2 of the mod, let me know if there are any more issues.