How are you values packed with the Matrix value receive?
The output of the actor is Text.
If you have something like 1,2,3,4,5 as the output from the Matrix Value Receive actor, that will be text, and will be sent as text when sent via OSC.
You will need to unpack the text on the PD side, and convert each numeric Text element into a float there.
How many values are you sending? If its a manageable number, you can send a bunch of numbers over OSC by using the OSC Multi Transmit actor.
Another option (if PD can unpack JSON) is to bundle your data as JSON, and unpack on the PD side.