Will I be able to get back in after getting out about 6 months ago, being barred from reenlistment, and having signed a dec statement?

Sounds like something doesn't add up here. If you were barred, then you weren't eligible to extend and there would be no declination to sign.
So, one of two things happened. One, you're confused about the terms and you signed a Declination and were ineligible to reenlist, not barred.
Or two, you signed a Declination and your command hated you so much that they barred you even though you were ineligible to reenlist. Meaning they specifically wanted to prevent you from joining the reserves or rejoining the active component.

Anything is waiverable, but good luck getting the Army to waiver someone who their commander barred just to stop them from reentering active duty.