Insight field smart search stopped working

[Rubèn C_]

We have an Insight field that no longer returns results when typing on it.

But it shows results when accessing to the values with the magnifying glass or when opening the drop down. It is just typing that doesn't work.

Problem is that this field contains thousands of values so smart search is key to use it.

Where could we start looking to know why typing always returns "No Matches" even though there are matches indeed?

Thank you.