Is there any way to be able to read sensors that handle CANopen protocol from the arduino mega, such as using mcp2515 to read CANbus, or does it work for CANopen?
It should work if connected correctly. I cannot see on the schematic which probably shows tons of reasons why it is not working. Post a schematic, not a frizzy picture. Also post links to each of the hardware devices showing technical information. I have several drawings of the MPC2515 module that are different but look the same and labeled the same. Also note the crystals values on the board. Also note how you have it terminated.
There is almost certainly a way. You either have to find someone you can copy or you will have to be the first. I would start with a Google search for 'CANopen Arduino' to see if there are existing libraries you can base your attempt on.