If your Sage 50 login ID and password are not working, there are a few things you can try to troubleshoot the issue:

Verify that you are entering the correct login ID and password. Make sure that you are using the correct case for each letter and that there are no extra spaces.
Check that your login ID and password are still valid. If you have recently changed your login credentials or your account has been suspended or deactivated, your login ID and password may no longer work. Contact your Sage 50 administrator or customer support to verify your account status.
Check your internet connection. If your internet connection is unstable or slow, it may prevent you from logging in. Make sure that you have a strong, stable internet connection before attempting to log in.
Clear your browser cache and cookies. Sometimes, your browser cache and cookies can interfere with your login credentials. Clear your cache and cookies, then try logging in again.
Try a different browser. If you are using a browser that is not compatible with Sage 50, you may have trouble logging in. Try using a different browser to see if this resolves the issue.
Reset your password. If you have forgotten your password or if it has been compromised, you can reset your password through the Sage 50 login page. Follow the prompts to reset your password and try logging in again.

If none of these steps resolve the issue, contact Sage 50 customer support for further assistance.