When using the newest version of the Link-OS™ Multiplatform SDK for iOS, a few developers have reported being unable to print images and/or text and receiving an “Unable to determine printer language” message.  If you encounter these errors, change the timeout on the MFi Bluetooth connection method setTimeToWaitAfterWriteInMilliseconds, from 10ms to a larger value like 30ms or higher to resolve the issue.
 
Here is an example of how to make this change:
// Establish the connection. 
connection = [[MfiBtPrinterConnection alloc] initWithSerialNumber:serialIP ];
// Change the the Time to wait after write from the default of 10ms to 30ms
        [((MfiBtPrinterConnection*)connection) setTimeToWaitAfterWriteInMilliseconds:30];