OTA port not showing up - but upload works

Hi all.
I'm using the IDE to upload sketckes via OTA to an ESP8266. It used to work fine, until two days ago the port selection dropdown stopped showing the available network ports.
However, since I last uploaded via OTA to the same IP, the last selected port is still in memory, so pressing upload still works, but againg, the available port selection is empty.
Any guesses/help?
Thanks