The pressure is too highthe AC line

Use the low pressure line to add refrigerant.

I was using the low pressure line to fill and the gauge said that the pressure was too high.

If this is true then the system may be overfilled or there is a compressor problem.

The system made need to be evacuated and recharged with the proper amount of refrigerant. Those install it yourself cans of refrigerant often cause more problems than they solve.

Also...was the vehicle running when you tried to put refrigerant in it? It needs to be running with the A/C compressor cycling.