Bernardo, by "can not enter" you mean can not register or can not log in using already existing account?

I have tried to register on your site but your CAPTCHA is not working, so I was not able to reproduce the issue.

Did you change the code or installed any plugings lately?

Hello Aliia, we cant log in, we dont do any change in the last days, but we have a lot of new users the last week. We try all, change the htacces, look the db, but all seems be ok, but some  pages give us 404 error and cant log into the community.

Thanks 

All the combinations user /password give me error 

No solution for this?

try to enable dev and debug mode in includes/config> save changes>f5 for the index page

Also you should check the server for the memory usage> try to delete many 500.phtml files (if you have so) in public_html of the server and another useless information

After delete check the ability to sign-in

I've experienced the same thing when activating one of the plugin. I sign in to cpanel.. create one folder and move the plugin file to the folder. 
then try to sign back into the site and success..

On my site email verification are not sent and after clicking sign in button it displays error , I have to approve the users and verify their emails in Admin :(

social.bazmeurdu.net

Nuqooshe,

Do not use other's post to discuss a new issue. Create a new post.

Bernardo, have you tried solutions from above?

cit24 what plugin do you activate which also this kind of problem so that we can be aware of it?