According to a source close to the band:
Passport issues: Ukrainians are high on the watch list apparently. Makes it difficult for them to get into the USA. This also may explain why he "can't be in a touring band."
@ashavildsen I left AA because I can't be in a touring band at this point of my life. There's no drama & I don't want to be a part of it.
— Денис Шафоростов. (@realdstoff) October 22, 2016
No Money: Denis is unable to come to the USA cause he's broke which surprising considering how many copies The Black sold.
The Document Speaks For Itself: Denis is under contract to Sumerian Records for two more albums. Who knows how these will be fulfilled.