After 5.4 update can't login from mobile phone

I tap the login or register button but nothing happens, so I cleared the cache with no change. Same for the rest of the members.

Thanks Hundiiiiiiiiii , I'll have a go at that.

Edit

However, Tom at CLS made a custom template for me for 5.2 and I have zero experience in messing with CSS and templates, so I'll check with him the correct way to handle this. Just updating the style may overwrite the template he made for me, I'm not sure.