Link Belt Quantum 2800 will not swing / rotate

got a call from cousin that has a Link Belt 2800/ Case 9040 last night from dirt pit saying Boom and Stick have hydraulics and operating, but the cab will not swing or rotate. Says it’s stuck in transport mode with boom facing forward. Any ideas where to start with this . From reading it looks like some folks say just needs to warm up, and other say hydraulic filter, or stuck solenoid valve.

Link Belt Quantum 2800 will not swing / rotate