Older web app will not run

I have a web app that I have not needed to look at in Xojo for over a year. The build is deployed and working just fine. I now need to make a modification and for some reason I cannot run it in the IDE. The …App Open event runs but if I put a stop in the Open event and step through it , it just quits without any errors or warnings as soon as I step out of the Open event. I am not sure which version of Xojo I last used but at the moment I only have 2019 Relseas 2 and 3 and it does the same thing in both.

Is there a log somewhere that might tell what is happening? What can i do at this point to figure what is wrong?

Get rid of or archive version 2019r2 and forget it ever happened

Use version 2019r3
Step through things in version 3

What OS are you having this happen on ?

I am using r3 on Mac High Sierra. I just used r2 as I had just recenly upgraded to r3 and thought it might be due to the upgrade.

yeah Xojo has completely withdrawn R2 so I would not use it at any rate
at least use 2019r2.1 (maybe thats what you meant ?)
But if you have 2019r3 stick with that

All that said its hard to diagnose whats could be going wrong without seeing the project itself
What port have you got it set to run on ?
That might play into it
If its < 1024 you probably will have issues

It was the debug port. It was set at 80. Changing it to 8080 fixed it. Thanks! All my other web apps have their debug port set to 8080. This particular web app is unique in the way the build has to be set to port 80 to work when deployed. I must have set it to 80 to mirror what was being done in the build. Strange that it worked on port 80 before. I did change routers recently.

port 80 would have more to do with it running locally on your machine or not