PT in Progress means that one of the WAEs did not see the SYN packet for the connection.
First packet the WAAS received redirected for the particular connection it was already in progress, so optimization could not get applied.
Open a new test connection via the setup and check if it gets optimized or not.
If it works, close the in progress' ones and open new ones as well. In case new connection also does not optimize, you will have to check the routing for assymetry or failure to redirect frames at both sides.
It is also possible that one of the WAEs reached connection limit for used platform and returns the packet untouched. Check the syslog for possible messages in this sense.
Andrej