My Nokia 5 (TA-1053) is stuck on the April Security Update. I've had not problem with any of the previous updates, including 8.1.0. I know the May and June Security Updates are already available for the Nokia 5, but mine keeps telling me my "system is up to date". No help from Nokia Support Chat.
Updates are released in batches based on location. You should be getting the recent June / July update.
Give your phone a restart and check for the updates. It should work.
Also, connect to a Wifi as the update size is large.
Nokia 5, Android 8.1 update was available from April / May.
Well, I already did several restarts and one factory rest, and it still reports no updates available.