The property ‘ValidValues’ of report parameter ‘TransactionsShift’ doesn’t have the expected type

I overcame the issue by making the below changes

firstly, to avoid having other runtime errors, if the dataset for the report parameter ‘TransactionsShift’ was automatically genereted, then unhide this dataset and go to dataset properties, replace the dax query with 

EVALUATE SUMMARIZECOLUMNS('TableName'[TransactionsShift])

then in the fields tab of the dataset properties window, delete other fields and only keep the TransactionsShift field and hit save.

next, go to Report Parameter properties of TransactionsShift, in the available values tab, select "Get values from a query", select the dataset you just modified above, and select "TransactionsShift" for Value field and Label field and save.

secondly,

navigate to the main dataset that you are adding the above parameter to filter dates, under Dataset properties, go to "Parameters" tab, click the "fx" button on "TransactionsShift" parameter and add the below expression and save.

= FormatDateTime(Parameters!TransactionsShift.Value,DateFormat.ShortDate)

Now when you run the report, you should not see the subject error.

hope that helps.