userId not found 400100

When I try to follow a user
Using this url
https://api.us.amity.co/api/v4/me/following/clbufsc8f185238urplxx8l1j


I get this error

Infact I have the User in the portal with the user ID

Hello, we could help check on this, could you pls provide us your full curls, apikey and region to our support email: support.asc@amity.co ?