Error Occurred: Internal Engine Error on Qlik Sense Desktop

[#1]

Hello everyone,

I have an app that has a pivot table and 2 charts. Whenever I try to filter the table based on the rows (clientName) it always shows this error.

Please see attached image.

Do you know how to fix it? It was working before, and for some reason it just started acting this way.

Any help will be appreciated. Thank you