Sorry to necro this thread but I figured I'd share. I couldn't connect to http://dlinkap.local when connected to the device's own wifi network on my Ubuntu 20.04 laptop, but I was able to from my Galaxy S9+ android phone. From there I could go through the set up process, connecting the range extender to my home network and getting it working again. So if anyone has issues connecting after a factory reset, try another device or two maybe? Good luck internet friends.
Model: DAP-1320A1