Server application unable to bind to a port

[ChaManO]

Hi,

Recently, after a reboot one of my servers has stopped working. It complains about not being able to bind to a port.
My setup is a Raspberry Pi3B running AArch64. The server is taskd, a Taskwarrior Sync Server which is supposed to listen at port 53589.
I've checked that nothing is assigned to that port with ss.
The server is run by user taskd of group taskd, and at the time the server stopped working the user was inactivated due to the raspberry losing hardware time and then reacquiring it (from 1970 to 2019 the account was probably locked due to inactivity).
I have deleted both the user and the group and created them again, but that hasn't worked. Running the server as root also fails to bind.
I have no idea what to look for anymore, so any tip would be appreciated.
Thanks