Sounds like an arial problem but to rule out a bad key, take your key to a good local auto locksmith and have them check the chip is working .
Takes a couple of seconds .We don't charge for this.
When you turn the ign on, the PATS light will be flashing rapidly.
leave the ign on for 1 min then read the code the light is showing you.
The light may blink once, then a gap, then 3 times.this is code 13 ( it could flash 1 and 5, or 2 and 4, or something else).
Let me know what the code is and I can give you an idea what the problem is.