I see a lot of issues here being blamed on using a Google account so figured it would be a good idea to switch over to my MS account whilst upgrading my phone. When I log out of my Google account in the app, it wipes all my data so I can't log in and sync with my MS account. There's an option to export my data which I can clean up using a json editor but no option to import it back in.
I switched over to SwiftKey from Swype (which I'd been using on my Symbian phone) a decade ago and being a Brit company I've been evangelical with my support for the app over the years. It has always managed to stay ahead of or at least keep up with the curve. However, over the last couple of years, it is increasingly playing catchup. I only notice the gap when upgrading my phone and having to temporarily use Gboard or Samsung Keyboard. With all the data you have collated and MS's AI knowledge hopefully you can shake off the cobwebs and get back on track or maybe next time, we'll stick with the default keyboard. Oh, the irony!