The TM-D710G memory space is a block of 1000 channels that can be accessed from either A band (left side) or B band (right side).
However, there's an obscure setting that may be causing you some difficulty. Check Menu 201, Memory Recall Method, and make sure it's set for ALL BANDS. If it's set to CURRENT, you'll only be able to recall memory channels within the current VFO band.
For example if the VFO on the right side of the radio is set to a UHF frequency and Menu 201 is set to CURRENT, you'll only be able to recall UHF frequencies from memory on the right side.