As far as specific ports I usually see 32767 on my end. For preview issues (especially ones that appear suddenly) usually either a change in proxy/security settings triggers the issue. To start, you’ll want your IT team to verify whether anything changed recently that would block Axure RP’s ability to generate a preview on the localhost at 127.0.0.1. If that seems all clear, then another thing to check would be that your antivirus tools aren’t blocking any specific files from loading. You can help check for this by previewing the page and then generating a HAR file to check for errors as specific files try to load. The link below has some steps on how to generate a HAR file in different browsers:
https://toolbox.googleapps.com/apps/har_analyzer/
When you generate the HAR file you can share it with your IT team, but feel free to email it to support@axure.com if you’d like for us to take a look as well!