Ok, I actually solved it.
When I connected my dropdown box to another datasource. For some reason, the DropDown1.Selected returned a result that was of type Record. I had to put DropDown1.Selected.Value in the Update property to actually get Text back.
Here is a bit more detail on the situation that I have:
I have an Edit Form that shows a number of cards from data source which is an Excel table.
One of those cards is called Project Status - when the app was automatically generated, this card had a Text Box where the user could type the project status.
However, I wanted instead of a Text Box, this to be a dropdown that only allowed several choices. These choices are defined in another Excel table (this is just a one-column table that includes the allowed choices).
To replace the text box with the drop down, I did the following:
1. Connected to the other Excel table through Data Sources - the name of the source was tblProjectStatus
2. Selected the text box and deleted it.
3. Selected the card, and inserted a dropdown (let's call it DropDown1).
4. Selected the dropdown and under:
a. Items -> tlbProjectStatus.ProjectStatus (that gave me the list of allowed choices)
b. Defaul -> Parent.Default
5. Selected the card, and under Update -> DropDown1.Selected.Value
Initially, in step 5 I only typed DropDown1.Selected, the powerapps didn't like the type of the value returned. It turned out that DropDown1.Selected returns a Record. Hence, I added the .Value to get a Text back.
I have followed your moves with this one, and in the edit screen, I can select the drop down etc. However when I save the edit card, the dropdown selection is not saved, even though I have set the update property as you have described. There are no error messages - just no update to that field of the record !!
I tried exactly what you said but it's not letting me set the Default attribute of the dropdown to Parent.Default neither the Update attribute of the card to Dropdown1.Selected.Value.
I tried to do it the other way around:
Default of the dropdown to Parent.Default.Value
Update of the card to Dropdown1.Selected
The warnings went away and everything seemed fine but at the moment of creating a new entry the server shows an error saying that a value is missing from the item (I don't have the exact error because my app is in spanish sorry)
My card has Default as ThisItem.EventName
It's Update value is: DropDown1.Selected.Value
DropDown1's Default is Parent.Default
DropDown1's Items are: ["A", "B", "C"]
Even if the value is B, DropDown1 will display default as A.
Not sure what I'm missing here. Starting a new project may be too difficult as I have a lot of time vested in this one.