Look at the features that prevent PowerApps running in a browser window
I developed two PowerApps that worked in a browser window for me as owner but when shared refused to run in a browser window and returned "The specified record was not found. Server Response: Execution Failure inner exception:...". It took trying iPAD Safari then Chrome to get the response "<My PowerApp> uses features that don’t work on a browser. To use it fully, install PowerApps Studio." Which did work. The Microsoft engineer did unearth some references but it is not well documented and still not explained why it works in the browser for the owner but not a user.