Thanks for using the Apple Support Communities. I'm a bit unclear on the exact issue you are running in to, but if you are having issues pairing a Bluetooth device to your iPhone, you may find the information and troubleshooting steps outlined in the following article helpful:
If you can't connect a Bluetooth accessory to your iPhone, iPad, or iPod touch - Apple Support
As there is no user access to the file management system on an iPhone it does not have the Bluetooth File Transfer Protocol (FTP) profile which I'm pretty sure is required for your scanner. This is for security reasons which are of paramount importance in iOS but not much in android. Check with the scanner maker and see if they have their own app that would allow you to used the scanner with an iPhone.
Question: I have an iPhone 8 and having problems Bluetoothing / pairing a OBD2 scanning to my phone and App. Android phones do this easy and have been told Bluetooth set up on iPhone not that good. Can anyone advise a way around this if possible. Thanks