The 5ghz WIFI have been at 0% signal for a while, and therefore not visible to devices.
I am using the stock WIFI antennas, and the 2.4ghz wifi is working just fine.
I believe you are trying to run Multi AP on 5GHz AND another 5GHz SSID at the same time.
My recall is vague, but you might need to choose to run one of them only.
I assume you already know that Multi AP is used in cicumstances when you are running ‘WiFi as WAN’ and the TravelMate support advice is to run your WiFi uplink (Multi AP) on one frequency e.g. 5GHz and your normal WiFi SSID for End User Devices on a different frequency e.g. 2.4Ghz.
Hello,
Your 5GHz interface has 0 clients, unlike your 2.4GHz interface, which has 12, therefore, there is no reference to evaluate the signal against:
It would show 0% for 2.4GHz if there were no clients as well:
Best regards,
Mike:
I have ran multi-AP but it is now disabled. Also I can not join any new wifi networks
Maybe so. If this is not resolved there will never be any clients! 
I think you may have misunderstood @Sigismundus point.
The Signal Strength of the SSID will always display as 0% when no clients are connected.
Even with Signal Strenth showing 0%, the SSID will still be broadcasting, and allow clients to authenticate to that SSID.
Only once a client has connected to that SSID, can the RUTX use the connection to calculate Signal Strength.
That seems to have been proven overnight! This morning the 5ghz wifi started showing, and when client was connected it displayed a signall strength 
But what does the error message in the top picture mean? “5Ghz radio already have one client”. Denying me from joining a “new” WIFI.
Hello,
You can only have one interface operating in Client or Multi AP mode on each of 5GHz and 2.4GHz radios:
Adding another Client or Multi AP instance will result in the aforementioned error.
Best regards,
Even if it is not active? So I will have to delete the instance completely before making a new one? That does not seem logical to me.