External candidate registration not happening

Dear All,

I'm facing a unique issue regarding external candidate registration. It was working perfectly some days ago registration, e-mail verification going to external candidate, after clicking that url they can create their profile also. After filling all required data if you click register button nothing is happening, but if you give any old user id or e-mail id then its showing already assigned; specify another one.

Our registration & start page is already live and lots of candidate had registered themselves. But now suddenly the registration url is not working.

My start page is working fine, already registered candidate can login by that logon page.

Some screenshot attached here for better reference.

Please help me to sort it out.

Best Regards,

Deeapk