Error when adding Spot to iOS Firefox

When I add Murena Spot as:
https://spot.murena.io/search?q=%s
to iOS Firefox and execute a search I get this URL: (search for iOS Firefox)

https://spot.murena.io/search?q=ios%20firefox

This’s seems ok?

The result is an error message:

Something's broken; we're on it!

We apologize for this unforeseen unavailability.
Our team is all hands looking at restoring our service as soon as possible.
During this operation, you will not be able to access the application, including any personal data stored in it. We apologize for the inconvenience.

This sounds as if this is a known issue?
But I tried it before a while ago and it was not working neither.
Is my search setup wrong ?

Any help appreciated.