XF 1.4 User can't login via mobile phone

Hi There, a lot of my user can not login using mobile phone ( Android and IOS ).

How to fix that error? Currently I used cloudflare for this Xenforo.

Thank you
Hi there,

I have whitelist some ip in Cloudflare.

Also, I made several trial in front end.
When I tried to login in front end, It successful. I could made several message and I could log out too.

But when I tried with the other username it would not login anymore.

This is only happen in mobile phone.

Is there anybody at here that found similar problem with me?