Couldn't load the data for this visual

JackPo There could be number of reasons for this error. Several people have experienced it based on different scenarios. You need to start by looking at the special features / calculations / tricks used in your report. To give you example

If you're using RLS in your report and have used publish to web for that report you will get this error.

If you have used measures and calculation of that becomes invalid then you will see this error (the way you will handle that is by using IF else so if values of calculation becomes invalid  you handle that). 

Sometimes using multiple data sources results in this issue.

I would suggest you start by checking RLS, then if you have special measures / calculations and troubleshooting further from the information you get.