Ok, 2 years plus dse901 user here, hope I can help! My first thought is "I wonder if he has a manual or auto battery?" and "Are the batteries still working?" Are you sure it's the attys and not the batts? If you have determined your batteries still work fine then---more questions!:
Are the attys making any sound or getting warm at all? Before giving up on them, lets see if they are only flooded. Take the atty off the battery and blow hard through it with your mouth on the battery end and a tissue loosely over the wick end to catch excess liquid. Do this several times. Did a bunch of liquid come out? Then it was probably flooded. Wipe off both ends and the end of the (fully charged) battery, reconnect and see if it vapes now (without adding more liquid). Anything?
If nothing came out at all- then it was too dry. Add 2-3 drops, wait a few seconds and try to vape again. Anything?
If neither "fix" changes anything the next thing you should try is cleaning your atty, it could be "clogged" but I'm doubtful of this since it doesn't seem like you've used any of them long enough for much to build up on them. There are many atty cleaning methods. Lately I've been using a pinch of baking soda in the wick end followed by a splash of vinegar, cover ends quickly with fingers so that the resulting fizz comes out the air hole. Do this several times then rinse under hot water and blow out your atty, rinse and blow 10 times. Let your atty dry out (manual battery dry burn/ perched on a lit light bulb for 3 hours/overnight on the kitchen counter- whatever!) When it's dry, add 2-3 drops only onto wick, reattach battery and vape. Anything yet?
If none of that works try gently prying up the center post on the atty/battery connection ends. You can use narrow tweezers, a bent paperclip, a dental tool- whatever that will fit in the little hole. Work your way around the post gently pulling up. This is to create a better connection between the 2 peices. Ok, now try to vape. Still nothing? Ok, it's probably dead...
How many drops at a time did you usually drip onto the wick? Did the attys EVER work? Did they work some and then stop? How did it taste before they died? By the way, I expect answers to ALL the questions! LOL! Good luck and let me know what happens.