Members only are un reblogable and there are a few people who do not understand the benefit of having their stuff reblogged who have unchecked this option in their blog.

Some members do not allow their posts to be re-blogged.  A

I have had that issue too - Looking forward to the answer

None of my posts are able since I am not a paying member - interesting since I've been here since day 1 LOL

Could have been members only or the author could have not allowed it when they published it.

It could be that the person is not a Rainmaker in which case their posts are all Members Only, or the author chose to make it Members Only. 

Looks like some good answers, wspecially from Bob Crane . I don't see that the age of the post has anything to do with it.

Glitches happen.   

Bob Crane answered two of the reasons I would add.

You can write what you would have written for a re-blog and post a link - the target post will still be "Members Only" if that was how it was classified originally.

Bob Crane has answered.

I'm assuming they were not Members Only posts?  Failing that, must be a glitch because age of post shouldn't impact reblogging.

Some members do not allow reblogs.

Some members do not allow their blogs rebloged or even comments. I do not think it matters how old is the blog post. 

Bob Crane and Ron and Alexandra Seigel I think covered it.

Peter Mohylsky - you are right - some old posts do not comply with current guidelines hence can't be re-blogged.

You may want to give credit to original author when you 'write' again as a new post....

Maybe they were Members Only, which can't be reblogged.

Rainmakers can select if they allow their posts to be reblogged or not. Rainers' posts do not allow this function.

     I see many current blogs that do not have "re-blog" enabled.   I'm not sure why some bloggers make (or do not make) that decision.

reblogging is very powerful..... you get google juice from it.... many bloggers don't realize that.... they equate it to copyright issues....

It can happen for a variety of reasons.  When that happens to me, if the author is a Rainmaker and it's not a members only post, I write an introduction and link to the full article.  

I will just rewrite it and submit if I think it is a useful one.

No there should be no reason but somone else said that wasn't working right either over the last few days.

Looks like everyone has beat me to the punch. Gotta be quick on this platform.

Member Only Posts cannot be re-blogged. Also, the author may be elected to disallow re-blogging.  There is a box to check before we publish our posts. 

Glitches or email the person to see if they would mind you re-blog their post.

This is where copy & paste comes in handy

In some cases the original blogger has disabled reblogging.

They didn't have a Rainmaker acct. ???

It could be because they are members only articles or the person checked (or checked) the reblog option so others can't reblog.  Or, a glitch.