Unless you created a backup somewhere . . . . .

There are some accounts I can't open these accounts now because cookies are deleted

When you return to those websites, new cookies would be created.

Please explain the problem in detail. What happens? What is/are the exact error message(s) ?

I did not create a backup .. but I want to know why the cookies were deleted I did not delete them Is there a way to get cookies back?

Cookies? No. But I don't think that is your problem.

Please explain the problem in detail. What happens? What is/are the exact error message(s) ?

There is no problem related to you and the problem is from me, but please help if any. Last Thursday, I was logged out of all the open sites on the browser. If there is a way to return cookies to the browser, I will be able to log in again to my site. Some of the sites that were logged out when you enter them again do not allow me to enter the site and said (we noticed unusual activity in your account) because of the deletion of cookies. Is there a way to return cookies or not? Noting that I did not delete cookies in the browser, they were cleared without any action on my part

Don't you have the credentials for the saved in the Lockwise Password Manager or otherwise have your logins saved as a backup, so you can log in again? If you do not have a backup and can't login then you need to reset the password for these websites.

There is not way to restore cookies that you previously used to make the website remember you if you do not have a backup of cookies.sqlite,