Most likely "tune failed". The dish has probably moved
You can't say that 100% for sure unless you can check it on another receiver.Dish is not moved, was working perfectly a day ago.
What are they trying to tune into when the message comes up?
Which tuner in use?
Which satellite?
Which frequency?
Any other receivers connected to the LNB?
I did have one of the tuners on my Zgemma H7S fail in the first week or two but I'm lead to believe it's fairly unusual (It was replaced FOC by World of Satellite).
You can't say that 100% for sure unless you can check it on another receiver.
If it's new note that not all installers fix dishes firmly enough. It might only take a pigeon to crash into it to move it a fraction of a degree which can be enough to stop it working or if it's mounted low down where people can bump into it.
It doesn't say the tuner has failed. It says it can't receive a signal on 11778. It could be any number of things - you are going to have to start be checking the receiver on a known good installation and you can also bring a known working box to try out. That will narrow things down.
What receiver did they have before this one? Was it a a Sky Q box?
When you go round, take your Enigma2 receiver so you can test it out. If your box works fine using the exact same cable, then there is an issue with their box. Also as a reminder, a manual & complete scan of 28.2 should find just over 890 channels.