I uploaded a new build to App Store Connect and started 7-day phased release. Before it was completed, I found out that there is a bug in it. I made a new build and now I want to upload it for a review with the same version number (let's call it 1.20) and only after the review will be completed I want to stop the previous rollout and start a new one.
But when I create a new release, I don't see the new build while it is in TestFlight. I can select only builds for the newer version (let's call it 1.21). What could be the reason of it? Alternatively, should I only upload newer versions of my app by incrementing the version within my build for each new release? In other words should I build my app with version specified as 1.20.1 instead of 1.20 that already exists?
Once a version has been approved by Apple and you have released it you cannot submit another build of that version for review.
You can upload a higher build number of that version for TestFlight but you cannot submit it for review and release it.
You will need to upload a higher version - 1.21 - and submit that for review and release it.
In general version numbers don't mean anything to users, so release 1.21 and move on.