If you used lightweight joint compound thats probably the reason, it dosen’t work that well for that. Ive been finishing for 27 years and its usually the amount of water in the compound, that isn’t there. Heres the correct way to do it. You have to put a litte water into the taping mud befor you put it on the joint. Do that and put enough of it in the joint so that the beveled seams and edges are full and level. Pre tear your tape for the length you need for that joint then apply the tape to the seam and knife it in pressing in firmly so the complete tape beds right. One of the most common mistakes is to let the joint compound set too long before the tape is applied. One of the first things a taper and finisher learns is speed is an essence, you don’t have to run but move fairly quickly so the moisture doesen’t evaporate out of the joint compound. You have to press in firmly to seat the tape especially on the butt joints. Always leave enough joint compound on the joint so that when you knife the tape in firmly it squeezes out from under the tape, especially on the squared ends of the sheetrock ends, an 1/8th of an inch on the butt joints is a minimum for do it yourselfers. The black lid Pro-Form bucket is the best for tapeing and textureing but the green bucket works ok too. The black lid is smoother, creamier and has more vinyls and glues in it, its a buck or two more but works better, thats all I use. The lightweight joint compounds are for the first and second topcoats over the tape after that has dried.
Did the bucket of Joint compound freeze because if it did it will loose some of its integrity. Don’t use the webbed tape, the paper tape is much better. The reason why is the paper tape offers more support and is a continous bridge on the joint whereas the webbed tape doesn’t, if the joint moves it will show cracking, I’ve done alot of repair jobs because of the webbed tape because it doesen’t offer any support, I don’t even know why they make it, probably because its easier to use. Send me a PM and we’ll go through what you did and we’ll find out what went on and what to do too correct it.