Looks like you have an invalid repo, and your version is a beta version, so, that’s why you cannot upgrade it.
You may download the current repo from the following link:
https://raw.githubusercontent.com/VitalPBX/VPS/master/resources/vitalpbx.repo
I cannot make you sure if you will be able to update from that old version to the new one, there are a lot of changes on newest versions.
