I purchased the Canon 90d when it first came out and loved it. It came with a canon kit lens with I found to enjoy as well. Wanting to move up some I purchased the 70-200 2.8 pro lens. This too worked great. HOwever, when I took the 2.8 off the body and tried to put back on the 135 kit lens, it won't shoot. Says Busy. Advice? I have cleaned the connections, taken out the batteries and SD cards for some time and nothing is working.
