Cannot Access wp-admin / Login Page Issue

Connect to the site via SFTP/SSH and check the debug.log file for any relevant errors.
If there are no errors in the logs, rename the plugins folder temporarily and try accessing the login page and /wp-admin/ again.
If an error points to a specific plugin, rename only that plugin’s folder instead of disabling all plugins.
Once the issue is identified, restore the folder name and proceed with further troubleshooting or plugin replacement/update as needed.

Symptom

Client or team member cannot reach or use the WordPress admin login.