Ive had this same problem. If you are using a regular keyboard where the "+" is above the "=" on the same key you have to acutally hold
control command shift +
because the plus is actually activated with the shift on top of the = sign.
If you have a keyboard with a 10-key pad on the side then you can use the stand alone plus on the 10-key pad and it will work fine without the shift.
Frustrating but it worked.