I tried to send a PM, but ...

[MostlyWater]

I tried to send a PM to a member but the system would not let me. I'd mention the poster's name but maybe I'm not supposed to.

What am I doing wrong ?

[FrankZ]

There can be a couple of reasons for this:

1) They are not accepting PMs (or only PMs from people on their friend's list)
2) Their PM box is full.

You likely didn't do anything wrong, it is likely issues out of your control.

[MostlyWater]

Oh .. OK. I got it.