Forum not providing backlink to linked websites

[crescendo]

Hello Webmasters,
I have created a forum on pharmacy related discussions. This forum is running since two years now. It is indexed and crawled by Google several times. But the problem is that it is not providing a single backlink to the other linked websites in this forum. Users have profile homepages and signatures too. But my forum is not giving any backlink to them. This forum has been created with phpbb. Is there anything missing like any setting in ACP?
This very problem is causing my forum users leaving my forum. Hopefully I will get help from my co webmasters. Thanks in advance for your valuable responses.

[RH-Calvin]

You need to check your Forum coding for this. There may be some coding errors which is causing your forum members not to have live links. You can contact your forum help.

[jane18]

Regular work is required at the forum for at least one or two years till it gets good page rank by online users.

[creativesquad]

check your forum linking either it set to be dofollow if its nofollow than nobody will get backlinks.

[Teamwork]

Thanks for sharing your thought.

[jamesnixon487]

Forums are limiting to give back links to avoid spammers.

[davidweb09]

It will give backlinks after some times, you need some more traffic.