This week I created a new PowerApps environment with a model driven app and I noticed one of the rollup currency field was not calculated. In this article I’ll explain the workaround to solve this issue.
To simplify the scenario, I have two entities: A and B. Entity A is the parent entity of B, so a record A can have one or more B child records associated. Entity A has the rollup attribute “Total Price”, which is the SUM of the Price attribute for the associated B child records. See below a screenshot with the same structure:
In that screenshot, the calculation worked, but that was after applying the workaround I’ve shared below. Just before that, this is the particular configuration for the “Total Price” attribute I have used:
Out-of-the-box rollup fields are calculated by a background process that runs peridocially (see more info here). I checked the background processes running the calculation, but it seems to be fine. I also tried pressing the “Recalculate” button in the form and that didn’t work either.
So what was the workaround to sort this out?
Just add the attribute “Currency” to the A (parent entity) form and set a value for one of the records: sorted it!
After adding the Currency attribute to the form, set its value in one of the A records and press “Recalculate”. That should show you now the calcualted value.
Once this has worked, you can hide again the Currency attribute from the form and everything should carry on working as expected.
Hope this saves you some time! 🙂
Note: this article is based on the following version Server version: 9.1.0000.6031 Client version: 1.3.1916-190625-161532
@ramontebar 
I looked everywhere and finally found your magic article that solved my problem. Thank you thank you!