Ok @Jules19
That looks like the Sky Hub not the Max.
Try a complete reset of your Q connection.
First reset your broadband router.
On Sky broadband hold the Reset on the back of the router until the power light flashes green (about 10 seconds). Don't unplug or switch off your router while it resets. The power light will go green when it's done.
Wait until the router is completely back and running and then try a Network Reset found in Q box Home - Settings - Setup - Network.
Highlight Status and then select Reset on the right hand side. Follow instructions to connect by WiFi to your router. Even if reset is not listed there is still an option to connect by WiFi to Sky or 3rd party router
On Sky Broadband you will be asked to press the WPS button on the Sky router. (Not on the Q box as the Network reset will start the main Q box WPS automatically). Make sure you press the WPS button on the Sky router and not the reset button.
Once the main Q box is back up and fully running reboot your Q mini.
To reboot press Standby on your mini remote (if the box responds to the remote), and then switch off and unplug at the mains.
Wait at least 30 secs and then Plug back in and switch your mini box back on at the mains.
Wait for the on screen instructions to disappear and the front led to turn Amber. Then wait for 30 secs before you press Home on your mini remote or if this is not working press the standby button on the front of the Q box (Amber led)
note: some features may take up to 5 minutes to return.
If the mini still does not connect reliably try a Network Reset on the mini.
Network Reset found in mini Home - Settings - Setup - Network.
Highlight Status and then select Reset on the right hand side. Follow instructions to WPS with main Q box.
You will be asked to press the WPS button on the main Q box (not the mini as the Network reset will start the mini WPS automatically).
If you are on Sky Broadband and the Router is nearer to the mini than the main box then you can try pressing WPS on the router instead of the main Q box. If you do this make sure you press the Sky router WPS button and not the router reset button.
Failing all of the above you may need a Sky Q WiFi Booster to position midway between your main Q box and the mini and you will need to contact Sky directly.
Edit
You have posted additional info on the mini.
If the mini is connected to the Sky Q WiFi booster
You need to first check that the booster is connected by WPS to the main Q box or router if nearer.
Then the network rest on the mini needs to connect by WPS to the booster