Can you check if your client is OIDC conformant? You can check it in the client’s settings in the dashboard, selecting your client and then scrolling down and clicking Show Advanced Settings. Under the OAuth tab there is a OIDC Conformant switch. In older non-OIDC Conformant clients, the id token will contain all the user profile, which may trigger this The generated token is too large. error. You can try enabling OIDC for your client, which will only return the standard claims back in the token and will not trigger this error.
You can read more about it here:
Applications in Auth0
ID Tokens
OpenID Connect Scopes