Hello dear, after registration, this error appears

Hi,

This might be conflict with any of the plugins you are using. Try keeping only social login plugin active just to confirm the same. If it works, you can activate other plugins one-by-one to check which is the one conflicting. Once we know which plugin that is we can work on the resolution of the problem.?

I have turned off all the plugins but still the same problem

Oh, then you would like to ask your web host if there is any service activated by them that is blocking the social login.