treating bottle refusal

I have a baby born at 26 weeks who was taking up to 10mL by Dr. Brown's ultra preemie once a day at the time of discharge and due to delays in getting therapy services started up, now will not take a bottle at all. He was DC'ed end of October and I started seeing him end of Nov and have yet to have him take the bottle at all. He lives with grandmother and she said at the beginning he would take it and drink the full 10 mL but then he got sick with a respiratory virus and hasn't taken it since. I've been recommending them to allow him lots of opportunity for oral play and very closely following his cues when attempting the bottle feeds to not cause an aversion. He's not in any distress at all when offered the bottle but he just has no interest in it. Any other ideas? I am planning to take the SOFFI course but hoping to get some help until I can do that.

edited to add- mom did not receive prenatal care until late in the pregnancy and baby was exposed to alcohol and unknown substance use, so far there are no known effects of that except the premature labor.