I am posting this in Aug 2023. I can no longer download Firehawk Remote app from Android on any of my devices because Google PlayStore says the app was made for an older version of Android. However, my old app on my phone still seems to work for the most part with minimal connection issues.
Today my phone stopped syncing to the physical unit even though it was connected by bluetooth and I could play other music through the unit. I tried all kinds of stunts, restarting app, restarting unit etc. What finally worked was clearing cache on the app itself.
So if your phone is connecting to the Firehawk via bluetooth but not syncing the presets, try going into the app setting from the android side. (Android>Settings>Apps>Firehawk Remote>Data Storage>Cache & Data and clear the cache as well as the data. This worked for me. When I restarted the app, it connected to my Firehawk, asked me to log into my Line 6 account fresh and synced like before.
I am leaving my experience here so that others with similar issues might benefit. Good luck!