I have a 21a I purchased about 18 years ago. It was reliable and very accurate. I put in the safe and pulled it out today, with the intention if occasionally carrying it. I kept having light strikes and failures to feed. I only took CCI mini-mags and Remington Golden bullets.
Do you have any recommendations on ammo to try?
I cleaned and oiled the gun prior to going to the range. I don't recall the ammo I used to use, but I know it was extremely reliable.
Thanks for the help.

Mini Mags should be your best bet in that gun and I’d stay clear of the golden bullet crap. I’d pull it apart as best you can and give it a deep cleaning and thorough lube job.

I had two FTFeed issues with mine: One was the ammo (only truly likes copper-jacked CCIs, no the the HPs), the other was the magazine.  I ended up taking the mag apart and used some steel wool to shine up interior.  It had developed a little corrosion in the corners causing the follower to drag randomly, then causing the round to not be lined up correctly.  Fires perfectly now even with some lead-nosed Federals (though those still screw up now and then).

I bet a good cleaning and changing the magazine would fix the problem.

This.
Use some solvent like Hoppe’s in the firing pin channel. Just a couple of drops. Work the pin back and forth many times.
Since the gun has been sitting up so long there is a good chance any oil or lube has gelled up.
Also put a couple of drops of light oil on the slide springs and exercise the slide also.
Those springs may be gummed up as well.