Sometimes this error appears

in this case you can check if you are connected with the correct credential

First of all you have to open power query:

From tab "DATA" click on query and connections, and than double click on on of the tables.

Click on " Data source Settings"

Highlight your source ad choose "Edit permission"

If you have " Organizational account " as credential, this is the cause of your error

Click on edit and choose windows, than Save

Now you can refresh the query!