OK, lets start again at a little different place.
EXAMINE the grooves you can see at the top of the retainer that are 90 degrees around the retainer from the set of grooves that stop short of the bottom of the retainer (that's the ones that are aligned with the dimples when the retainer is normally assembled) when part of the retainer is protruding from the mag tube. MAKE SURE those not-aligned-with-the-dimples grooves are clear, clean, unburred, etc at the top and down as far as you can see. Use a needle file to clean them up back to original depth/width if they are frizzled, boogered or otherwise obstructed. NOTE the position of those two grooves and remember which way to turn the retainer to reach them.
IF none of the retainer is protruding above the top/end of the mag tube when in its normally assembled place, your problem is not in lining up the grooves. Likely the end of the mag tube is damaged/crimped/bent/out of round and that is what is holding the detent down, not the dimples. If this is the case, you need to STOP and get professional help NOW. A gunsmith will have a properly shaped mandrel that will let him 're-round' the magazine tube without doing further damage. And there is nothing you can do at this point that will not make things worse.
IF about a third or half the retainer protrudes above the top/end of the mag tube when it's not pushed down, and you have cleaned out the grooves you can see, THEN:
1) Push the retainer down past the dimples
2) Turn it just a bit (a fraction of an inch) and let the spring push it back up against the dimples till it stops
3) Turn it s l o w l y while it's in contact with the dimples, NOT pushing down, just turning, turning it toward the direction of the second set of grooves you could see while the top of the retainer protruded from the mag tube
4) Let the mag spring push it out, while you control it against the spring's pressure to avoid letting it leap across the room. About 8" or so of mag spring will come out of the mag tube once it's all free. It'll hurt you if you aren't careful.
hth,
lpl