VRCExpressionParameters has too many parameters defined.
Every avatar has a max limit of 256 bits of memory usable in the expression parameters. Your avatar is using too much memory, or does not have enough left for whatever feature you’re trying to add.
If you click on your avatar, and scroll down in your Avatar Descriptor, you can find your Expression Parameters Double click it and it'll switch to show your expression parameters and show what's using it up
If you have blanks, just delete those. Otherwise you'd have to remove other parameters but that may make certain things stop working