VOIP Problem with new router

I wasn’t sure where to post this so here it is. I recently changed routers from Linksys WRT54GL to Linksys WRT1200AC. The 1200 is using factory firmware. I cannot make VOIP calls through this router. After just a few seconds, I get a “No response, timed out” error on my phone. I can reconnect the WRT54GL and it works fine. Am I missing something in the router setup? I only changed the IP, password and wifi security phrase to match the WRT54, or is there a phone setting that I need to change? Can anyone help?

Thanks for the response. The link is gibberish and does not address my problem.

when dealing with Router setting it can get complex fast
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