1) Log into your LJ. Pretend your LJ name is Applepie. This means your LJ homepage will be http://applepie.livejournal.com. I will use this fake non-existent personal lj as an example so that you can see what to do.
2) Go to http://www.livejournal.com/manage/settings/?cat=notifications
3) Scroll down until you see the words "SOMEONE SENDS ME A MESSAGE".
- Make sure the option is ticked under "email" and "inbox"
- Now, scroll down close to the bottom of the page until you see the words “Friends and Communities Notify me when..”
- Make sure the options for “ I receive an invitation to join a community” are ticked.
- Now click “save” to save the changes.
4) Now, start from your LJ home page of http://applepie.livejournal.com/
- now type the word "profile" at the back of that address so that it says this http://applepie.livejournal.com/profile
- press enter
- you will now be at your profile page.
- look at very top of the page, next to your user icon. see that there are many words to the right of your user pic?
- look for the word "profile" and click it. you will be taken to a new page
- after that, scroll down and look for "Contact Info"
- after that, look for "LJ User messaging". That part should say "receive messages from" followed by a a drop-down menu of choices.
- in this drop-down menu in THIS PART ONLY, choose "registered users" meaning that anyone with a registered LJ account can PM you.
- after that, scroll down until you see "save changes" button. click it.
5) Check your LJ inbox daily. You must do this because LJ can screw up a lot. It can send messages in places that are NOT your inbox.
- do this whenever you log in each day.
- after logging in, go to your lj profile page.
- your lj profile is the one that has the "profile" word at the back.
- you do this by starting from your LJ home page of http://applepie.livejournal.com/
- now type the word "profile" at the back of that address so that it says this http://applepie.livejournal.com/profile
- press enter
- you will now be at your profile page.
- look at very top of the page, next to your user icon.
- somewhere there, there will be the word "messages"
- click on that
- look at the left hand side. you will see words like "all", "messages", "friend updates" etc.
- because LJ screws up a lot, you must always check the "all" and "suspicious messages" and "entries & comments" folder every day.
- this is because LJ often thinks that messages with emails, urls etc are spam and they will put them in "spam" or "suspicious messages". when this happens, you will never ever get notification and you will never know that someone really did send you a PM or commented to your LJ entry or reply to you when you comment in a locked comm etc.

Thank you so much for taking the time to write this dear, I've linked to your comment in both entries about the issue :)

thank you for sharing :)