question

I have not seen that popup message before, so I don't know how it relates to licensing, but in general:

• The lmgrd port needs to be allowed through any firewalls between the client PC and the license server. Our default port number for lmgrd is 26914 if you're following our license server installation instructions.
• The vendor daemon port also must be allowed through any firewalls. Our default port number is 56914.
• You can text connectivity between the client PC and the license server by using telnet to test. Be sure to test both ports.

If you can connect across both ports from the client PC to the license server, then this popup may not be related to communication with the license server. In that case, please test:

• Does double-clicking a model file to open it directly (bypassing the start page) avoid the error? There is a chance that the start page's network activity across the VPN could be causing the error.
• If a double-clicked model opens in FlexSim just fine, you may want to disable the start page communication. This can be done by unchecking all the options at File > Global Preferences > Dynamic Content.
• The start page can be disabled altogether, though you then lose the easy-to-access list of recent files and the quick-start buttons for licensing, preferences, etc. If completely disabling the start page is desired this can be done from File > Global Preferences > Environment > Show start page when FlexSim opens.

Let us know what you find out.