Help! My Attenuation sucks

I need help figuring this out. I have done everything I can think of to fix this but nothing seems to help. No matter what I do my beers seem to finish at about 1.020. I do 10 gallons batches, use oxygen to oxygenate, use 2000ml starters, have conicals, I have temperature control for the fermentation. it doesn't seem to matter the starting gravity, ale, lager they all seem to end at about 1.020. I have also tried other hydrometers. any help you give would be greatly appriciated

Are you brewing AG or extract or does it not seem to matter? Also, you said that you use temperature controlled fermentation. What temperature schedule do you use? It's also possible that you're under-pitching. I generally pitch a 2L starter in a five gallon batch. I don't do ten gallon batches but it seems that stepping up to ten gallons would be better. Have tried doing a larger starter or pitching 2-3 packs of dry yeast?

Go listen to the brew strong podcast about attenuation....good stuff. Will teach you everything you need to know

what yeasts do you use? Dry vs Liquid etc

Yeast strain, malts used, mash temp?

What's your water like... zinc or other nutrient deficiency can also be a problem, yeast nutrient (yeast hulls) may help if your water is low in zinc or you are using distilled bottled water.

If you're doing all-grain,what temperature are you mashing at? The higher the mash temp,the less fermentable sugars you'll have.150 to 154 should end at 1.009 to 1.011. 155 to 158 should end at 1.011 to 1.013.These are approximate but you'll get the idea.

I do all Grain and depending on the beer I will mash anywhere between 148 to 154. and I do have a RIMS system. For our ales we usually use english 2 row pale malt usually muntons. for lagers we will usually use a german lager or pilsner malt. for our ales we use white labs british ale yeast or Irish ale yeast and for our lagers we use white labs german lager yeast. but none of those things seem to matter I have tried changing things but they all seem to finish about the same at about 1.020. as for fermentation we have fermented ales for as long as a month and still don't drop. and I also use servomyces yeast nutrient

Ok......2000ml starter,that's just over two quarts.Yeast slurry from a one gallon starter is recommended for five gallons,I think I'd try increasing that for a start.Have you tried pitching in more yeast?Don't aerate it,just throw in some more yeast.
Your using conicals...there is a thing called CO2 toxicity that will kill off the yeast if it builds up too much.Is the CO2 escaping freely from the conicals?
Are you giving it enough oxygen?I'm on the fence on this one though,I've made batches with barely any aeration let alone using oxygen and they fermented just fine.
First thing I would try is bumping up that pitching rate and make sure the fermentation temps are not too low.I haven't used White Labs but with Wyeast the temps have to be at least 52 deg.for lagers and 68 deg. for ales.
One more thing,you shouldn't have to use yeast energizers or enzymes on a regular basis.I've never used them.

I've found that the WLP002 (which I use a lot) sometimes settles before the fermentation is finished. A good rousing usually fixes this, but it only happens occasionally, not every time.

-a.

Try a fast ferment test in parallel to your main batch next time.
Fast Ferment Test - German Brewing Techniques
Just take a pint or so of wort, stick it in a jar, and dump in a teaspoon or so of bread yeast. That's WAY more than enough yeast for the wort volume so it'll ferment fast and ferment out as completely as the wort allows - that way you will know if your high FG's are due to a high level of unfermentables in the wort, or due to the yeast not finishing the job. Then you can take appropriate steps to remedy it either way.