If not sure wich plugin is the offender, use FTP or server file manager to temproarily rename the plugins
folder, log in, visit the plugin page and all plugins is automatically deactivated.
If this doesn’t help, and you have modified an active theme, using the theme editor, then temporarily rename functions.php of your active theme folder.
If this doesn’t help rename the folder of your active theme. It will then force WordPress to use the default theme.
If this doesn’t help either, reinstall WordPress manually using FTP and remove all themes form themes
folder, except the “twenty ..” ones.
See also https://codex.www.ads-software.com/Troubleshooting