It seems the R 0.21 update for the Pixel4a “sunfish” is available here but the System device/update OTA is not finding it showing “No new updates found”. Could this be a server issue or is the update not yet available via OTA?
I think 0.21 upgrade is beeing released, and servers are overloaded.
Same happens on my Redmi Note 7 Lavender (currently on R 0.18), “Failed to check for updates, please verify your internet connection”
Otherwise I can manually update it from here: https://images.ecloud.global/dev/lavender/