First try clearing your cache and see if that makes a difference. If not, you might want to try restarting your computer.
If these do not correct the issue, your network or firewall may be causing this issue. Please check with your IT department and assure that it is allowing all requests from any submittal123 domain to go through.
If that doesn't take care of the issue, you may contact our support team and we will try to help, but we can not help with our client's internal network/firewall issues.
Follow this link for instructions on clearing your cache: