Sorry to be a pest but I have had this problem a few times and would rather not “workaround” it by bouncing the Raspberry Pi.
The symptoms are that any page shows only the blue banner with no text. SSH is unresponsive but I can ping the system.
This Windows10 PC does not seem to understand telnet and I suspect that Hassbian would have disabled it in any case. The implementation is headless as the Rpi lives in the garage next to a ground source heat pump and HA monitors that heat pump.
As ever, any help gratefully received as the system has only been up 24 hours since I had to reboot it due to the same condition.
I could connect a TV to the Rpi but that would be a right pain and I suspect it would show me nothing.