CQD & AA on Teams report refresh randomly fails due to null responses

[Anonymous]

I published the CQD en AA power bi template to get insights in our Teams usage.

When I "developed" it, the report refreshed successfully on power bi Desktop. Then I published it to Power BI online.

The report ran perfectly for 2 weeks on our Power BI Online environment but now it failed for 4 days in a row. 

As I looked into the issue in the Power bi Desktop, I couldn't refresh it their neither:

• There is always one of the queries that fails, resulting in a null response, on which powerbi throws an error.
• Which query that fails is random: every time I do a new refresh another query seems to fail.
• I got the error: We cannot convert the value null to type List. Because the response is null.
• I can preview all the results: the queries do work on by one.
• I already cleared and re-entered the credentials, which didn't seem to help neither.

Did anyone already experience this issue? What can be done to let the report refresh again?

Thanks!

[Anonymous]

Thanks for your reply already!
I had a look already to that kind of issues, where there are errors popping up during a transformation, but this is not issue in my case. I just receive a general "null" value as a response, which cannot be transferred into a list. Raising an error.

Best regards, 

Axel 

[V-lianl-msft]

Hi @Anonymous ,

The error message means that you need to change null value to other values when you change data type.

You can refer to this thread to solve such errors:

https://community.powerbi.com/t5/Desktop/Cannot-convert-value-null-to-type-List/m-p/893014 

Best Regards,
Liang
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.