Tendinitis takes a long time to come on and won't simple go away with some rest. It is small micro-fractures at the done-tendon interface. You need to discuss what you were doing in the many months leading up to the injury e.g. footwear, playing surface, types and amount of training, diet etc etc. Then assess your biomechanics and more. It is not as simple as rest and it will go away.

Additionally if all is considered normal then the tendon/bone is breaking down (or not healing) for another reason. Our tissues breakdown and repair all the time. It could be that yours is failing in its repair phase (often diet). This can also be because another body system is less than optimal and is blocking that pathway or 'stealing' from it in some way. In my experience applied kinesiology can provide some insights into that and can suggest potential diet restructuring to assist.