I have a process builder which I want to build to production, when I create a change set it says that this change set requires the "45.0" or later platform version, if it was a visualforce page I could change the api version, but I couldn't do that for the process builder, how can I accomplish that? The production runs in 44.0 api version and my sandbox in 45.0 api version.
Please refer to this article from salesforce Version error when uploading Change Set
You might just have to clone your change set and try deploying again.
Best Regards, Amit