Group By showing expression error

[DonnaDonut85]

Hi guys,

Hoping you can help. We have a Power BI report which was created by someone who has now left the company so i am trying my very best to fix an issue but i am a total beginner and unfortunatly we dont have anyone else with Power BI expertise.

The reports have been set up about 10 months ago and were working fine until last month when they stopped refreshing due to this error 'We cannot convert the value null to type Logical' 

I have downloaded the report and opened in Power BI desktop (it will not referesh - same error) I have then opened Power Query and i can see a lot of errors but i think i have whittled them all down to once particular change that was made. There is an attempt to group 2 columns, the user title column and the week of year column. I can see it doesnt like, i checked to see if there were any null values in these columns and there were not, but this still doesnt load. I then changed the valus to replace null with "Unspecified" in case i hadnt loaded all the data, but still no joy. 

Can anyone shed some light? I'm confused on why this report would ever work if this error was always there - or is it maybe the data? Even though i have replaced values and made sure there were no blanks? The formula is = Table.Group(#"Filtered Rows", {"User.Title", "Week of Year"}, {{"Sum", each List.Sum([Hours]), type nullable number}}) 

I would appreciate any guidance on this - thank you! 

[amitchandak]

@DonnaDonut85 , this seems fine. But there are too many error tables there. can check all and remove their errors too.

[DonnaDonut85 · Accepted solution]

Thanks @amitchandak but they all reference the "Sum" column and or the "Timesheets -WeeklyBasic" table so it looks like once the error is fixed in "Timesheets - WeeklyBasic" then the rest will be ok.