Hi @AlanBo,
Could you please share a bit more about the issue within your app?
Could you please share a bit more about the Dropdown menu that you mentioned? Is it a Combo box control?
Further, could you please show more details about the data source that you mentioned? Is it a SP list data source?
The user @calvares and @AlanBo has faced similar issue with you, please check the following threads:
https://powerusers.microsoft.com/t5/Connecting-to-Data/Person-drop-down-not-displaying-names/m-p/152011
https://powerusers.microsoft.com/t5/General-Discussion/Searchable-Dropdown-in-datacard-doesn-t-work-in-mobile-version/m-p/151872#M51590
I suppose that the data source that you mentioned is a SP list, and the Dropdown menu (Combo box control) field is connected to a Person or a Choice type column within your SP list, is it true?
I have made a test on my side, and don't have the issue that you mentioned. Please check if the version of PowerApps Mobile App within your Mobile device is the latest version, if not, please upgrade it to the latest version, then check if the issue is solved.
If the issue still exists, please take a try to uninstall the PowerApps Mobile App from your Mobile Device, and then re-install it again to check if the issue still exists.
Best regards,
Kris