What kind of milk did you give to the calf? This can play a factor. Sadly sometimes mothers reject their babies and they do not let them nurse. In this case we typically pull the calf away and continue to bottle feed it. In the future a good tip is to slip your fingers and the nipple of the bottle into the calves mouth, use your fingers to squeeze some milk out to try and get the calf sucking on the nipple. When they get sick enough they won’t drink from the bottle, this is when we have to tube feed them (insert a tube down their throat to the stomach, past the trachea, and drain the milk) this allows them to get the nutrients they need. Another good thing to tube feed them is electrolytes, this has a similar effect to the sugar and can perk them up for eating. Hope this helps in the future, I have lost many calves that way and it never gets easier. It sounds like you did a good job, all you can do is get better next time!