I just looked up the RT29, I should have done that before answering. If what I saw and read was correct the RT29 has no screen. As paulears asked, are you sure about the Retevis programming?
My church has four Retevis RT21 radios that also have no screens. They were purchased years ago from a radio shop that is no longer in business. All four radios would talk to each other. At one point while using one of the radios I could hear other traffic. They could not hear me or at least refused to respond. I used an inexpensive frequency counter that also shows TX ctcss and dcs tones. All 16 channels were GMRS frequencies with random ctcss or dcs TX tones. The church also has four Cobra brand FRS/GMRS bubble pack radios. I was able to use the counter to determine what the tones were and then eventually determine which channels and tones would allow all 8 radios to communicate.
The point of all of this is that unless you have programming documentation for the Retevis or performed the programming yourself you won’t know what frequency/tones you are dealing with. Our professionally programmed Retevis radios had tones on every frequency, and once I was able to determine the frequencies I found they were not in the normal GMRS channel order.
Using a frequency counter or another radio that has regular scan and tone scan would make troubleshooting much easier. Otherwise you will need to try ever combination inputting all ctcss and dcs tones one at a time until you find the magic combination. It can be done but it will be tedious and probably time consuming.
