You may have to pull the joint apart because if you hadn't greased it often enough, the grease can get solid and hard pack, in which case you either need to have the joint pulled apart completely or you need to have a high pressure grease delivery system to force out the solidified gunk that's blocking the grease from being injected.
Discussion
Was afraid that might be the answer. Looking into pressure systems too. Heard there might be a grease gun you use with hammer to break it free. Waiting on my Mexican tractor. mechanic answer. They deal with stuff and amaze me with their tricks. Thanks for answering 🤙