Mission Planner/ APM Planner not connecting with ardupilot

Dear friends:

I have started using Ardupilot with mission planner (I have a mac but I installed windows with parallels ) and it started working. First I updated the firmware to the APM 2.6 and then I connected the port with 115200 rate.

Now I have problems with the connection, it appears a message “Time to connect . Timeout in 30.29…1” and then “only 1 heartbeat received”. I have tried to reinstall the Mission planner and with other versions of this software, but still not working.

I then decided to install the APM planner because it can be used with mac, but I have an error of the same style when connecting. It remains downloading parameters but not working.

Do you have any idea? I have seen on many forums, but they don’t say anything clear.

Many thanks!!