Grizz Chapman, the actor best known for his work on “30 Rock,” died yesterday … and now we’re learning a little more about what led up to his passing.

Renee Glicker, Chapman’s manager, tells TMZ … the beloved film and TV actor has been suffering from an assortment of medical conditions in the past few years … and was “just struggling to stay alive.”

Chapman received a kidney transplant in July 2010 … and Renee said he needed another transplant … but given his enormous size — he stood 7-feet tall — finding a match again was difficult.

His exact cause of death is not clear … but his manager suspects there are a number of contributing factors.

In addition to his work on the NBC series … Chapman created a series of YouTube videos known as “Grizz Chroniclez” featuring him in a variety of sketches.

The actor appeared in several other films, music videos, and TV shows, including “Blue Bloods” and “The Blacklist.”

Chapman is survived by his ex-wife and their two children.

He was 52.