Lister had been experiencing COVID symptoms in the days leading up to his death ... according to his manager, Cindy Cowan.
Cowan tells CNN that Tiny began feeling sick a week ago, but he got worse quickly -- couldn't breathe and felt very weak.
She says he was supposed to work on a movie set last weekend but had to cancel due to his breathing difficulties, and he also canceled a Zoom appearance for a TV festival Wednesday. That night is when Cowan says friends and family tried to call and check on him, but their calls went on answered.