It turns out I got into a similar situation. I've upgraded several routers, ours and clients, to 2.4.4 and 2.4.4_1 recently. Last night I tried updating a SG-3100 from 2.4.3_1 and the GUI kept showing a "failed" message during the update and/or downloading, but no actual errors were shown that I saw. I tried a couple of times, and eventually it finished, and restarted, but didn't come up. Today on site I could not ping the LAN IP showing in the console, and the console showed 2.4.4_1 installed but all sorts of PHP errors for missing libraries and so forth (I didn't document them). The short version is I ended up reinstalling from the SG-3100 "factory" image for 2.4.4_1 (https://www.netgate.com/docs/pfsense/book/install/download-installer-image.html) via USB stick and it seems fine now.
A while back I seem to recall someone posting that the update could "fail" but still be processing in the background and the router restart eventually and upgrade fine...I'm wondering if something like that happened and I didn't wait for the reboot.