Hello,
If you wait for the SSID to appear, does it never come up until you disable the wireless client or it manages to appear after some time?
If SSID appears after a while, then is standard router's behavior since that happens when router is scanning the added WiFi networks, while the router is doing that the WiFi service is being restarted and the router will not show a SSID until stops scanning. This can take up to 5 minutes.
If that is not the case, could try to reset the router to factory settings and just try to add the same WiFi networks to the router and see if the issue persists. The instructions for factory reset can be found on our wiki page.
Before starting the factory reset procedure you can download backup of your current configuration, which you can later reupload to the router if needed. Go to WebUI System -> Backup and look for section Backup configuration and press download. In the provided wiki link you can also find the steps for restoring the configuration from backup.
Regards,
Paulius