A/C Won't Take Freon Volvo 2003 C70

What is your question?

I just purchased this as a used car. I attempted to put in A/C Pro refrigerant. However, the car would not take it. I called A/C Pro technical service and was told it is a mechanical problem. While attempting to put in the Freon, the compressor and a/c was running with a full connection on the low port. However, the Freon didn't go in. I exchanged the a/c pro product back to the store in case it was a faulty can but I had the same problem. Please help me what direction to proceed forward. Thanks.