Pairing problem NAS326

I accidentally unpaired my NAS 236 from my cloud.zyxel.com.
Now, when I try to pair, I start "search", then "Manually Add" and enter the MAC and serial, and when the search starts, which should last 10 minutes (from which time I need to press the button on the device), the peocedure stops after 5-6 seconds and I get the message "Device not found".
Before accidentally deleting the pairing, everything was working fine. What's the problem?