Thanks for the quick reply. Sentinel literally will not run anymore. Worked fine then not.

Did you get it worked out?

Seems so. This is/was a problem with dash too.

https://www.dash.org/forum/threads/cant-detect-valid-external-address-unable-to-start-mn.13233/

Apparently if you are behind a NAT, the masternode can't "talk" to itself to verify the external IP. I had to add my external IP and an alias in windows.

https://www.ibm.com/support/knowledgecenter/en/SSMMM5_8.1.0/com.ibm.rational.test.lt.doc/topics/tconfigip_win.html

Hope this helps someone with this problem.

Thanks for the update, and glad you got it worked out! I will keep this in mind next time someone has an issue with it.