How to find out which plugin create captcha after login?

This looks like LiteSpeed reCaptcha – https://blog.litespeedtech.com/2019/03/18/recaptcha-server-wide-protection/

Probalby it was enabled by your hosting provider to protect sites from brute force attacks. I’d suggest you to contact them and explain your issue so they could configure it to make a proper redirect after reCaptcha check.