Dual A/C problem-rear blows cold, front does NOT

I have a 99 suburban with front and rear a/c.
The front a/c does not blow cold, the rear does.
I have had to add a can about once per year for several years now. Always has made v cold air after trimming the charge.
Compressor seems to cycle on and off as expected, not frequent as if low on charge.
Added a can today, reached steady state pressure circa 25#, still no cold in the front, no change to the rear, still blowing sub 60F air.
The recirc control damper is working fine too.
The temperature contoller working normal, three.
The floor/vent/defrost controller working normal, fore.

Anything simple/easy to try, or do I need a pro?

check your orifice tube in the front or it might be an expansion valve or some other filter. I had this problem with my 95 when I replaced the rear expansion valve. Basically my original compressor shot to bits and sent crap through the system and plugged up the rear valve. When I changed it out, I only flushed the lines going to the rear, I forgot all about the front system. Long story short, the plug moved from the rear to the front and I had to once again open the system up and do a complete flush of both the front and rear lines as well as change the filter/orifice tubes in the front. Now the A/C works great. Around 60 degrees for both front and back.

Supply both low and high pressures after running a few minutes, at 1500 rpm.

"I have had to add a can about once per year for several years now." It's obvious you do have a leak; I think your leak just got worse than before. Supply your pressures. My own '94 leaks at the crimp on the high-pressure line.