i don't have the gt score for 17c but I have a master degree in Cybersecurity, can i reclass to mos to 17c?

With a master in cyber you might be better off accessing as a Warrant or direct Commission but you'll still need a 110 GT.
If you want to enlist into that job you can contact the MOS proponent for a GT waiver. If it's only a few points off you will probably be granted the waiver

If you don’t have the GT score for 17C, you can’t reclass into 17C.

You must complete the FAST/AFCT class and raise your GT score to be eligible

You need to contract someone at Cyber branch. I worked with an NCO that didn't qualify for Cyber but he went out on his own and get all of the Certs you would get if you were to go into Cyber. They gave him an ETP and sent him to WOCS and he became a Cyber WO. They are looking for Soldiers with experience. If you have it they might make an ETP to access you.