Restore access to WordPress dashboard on client site

This WordPress site (53 pages for an engineering firm) was hacked, but we cleaned it and ran scans with WordFence. We upgraded to WordPress 6.0, but now we cannot get into the Dashboard. It seems to accept our login, but keeps us on the login screen. There are backups on the server, and backups in Dropbox (through Updraft). We tried disabling WordFence with FTP, but that did not solve the problem. Corrected a few file permission settings also.
We need someone to try the other approaches and restore access by the night of July 30, 2022.