We get this error(Attachment) on first startup of application for ios after publish new application version. But we can open application after a few attempts. There is no problem for other platforms (Android,Web).
Error: This app isn't opening correctly. Session ID: 8d68b359-ea70-4064-90f0-1b9095e79d68
Do you mean that this error only occurs within your iOS device?
Please check if the PowerApps Mobile App in your iOS device has been upgrade to the latest version, if not, please consider upgrade it to the latest version firstly, then try it again, check if the issue is solved.
Please consider open your app, and made some changes to it (e.g. add a button, then remove it), and turn off the "Improved app rendering (final validation)" option within Advanced settings of App settings of your app, then re-publish your app, check if the issue fixed.
Also please consider take a try to re-store your PowerApps app to previous version, then made some changes to it, and re-publish it again, check if the issue is fixed.
More details about re-storing app to previous version, please check the following article: