I am working on a WordPress website for a client. They have the website hosted on IONOS and we are getting these frequent problems. There are files missing from time to time which causes to get a critical error, after I get the missing files and put them in the correct folder we are unable to log into the page. Also, the last time I have added the missing files a textbox with a submit button appeared on the top of the page and moved the top menu down. I am getting this error on the /wp-login.php page (Error: Cookies are blocked due to unexpected output. For help, please see this documentation or try the support forums.) and nothing else. When I try to reset the password it sends me the link but I am unable to change it or do anything else. Any help regarding this matter is appreciated.
As I've explained before I am uploading the missing files, yet this happens again and I am trying to figure out why it does and how it does so that I can prevent it from happenning. Also I am now seeing that the url for logging in has changed from (https://example.com/wp-admin/) to (https://example.com/wp-login.php).
Best regards, Hristijan. :)