To optimize storage space, the images server keeps only last few builds. It is usually last 5-6 builds for most devices. When new builds come up the last ones are removed.
However the posts that follow show that an phone on 0.19-o-20211023142277-stable-starlte
did receive the OTA upgrade, it may or may not be related but in early attempts to troubleshoot the “wifi connection” issue the router was reset. However the captiveportal_urls solution above may also bump the System updater into action, perhaps.