Hi @omazoneea_oneea
Have you made any changes in Cookies setting? If yes then undo those changes and flush the cache and verify the website again.
Also, sometimes it occur due to less space on server side. So try to remove some unnecessary like which stored on Var folder. I faced same issue on my staging server once and it was due to less space on server side. So please check and let me know if there is anything else.
if issue solved,Click Kudos & Accept as Solution