XF 1.5 Like button missing for some members

I have a strange issue where three of my members are unable to see the "like" button.
I have talked them through the usual procedures (try another browser/clear cache/try another theme etc.) but they simply can't see them.
I have checked their usergroups/permissions and all looks good.
This has happened since I upgraded the server to PHP 5.6
Any ideas?
An update.
I have been able to log into the forums as a couple of the members (they kindly gave me permission and passwords)
The situation is this: four of the 350+ members see the like button on all posts posted more than three days ago, but if there is an OLD thread but with a new reply they DO see the like button on all of the posts in that thread.
All the other members can see the like button normally on all posts.
I am so confused. I have re-checked permissions, using diferent themes and I can't for the life of me see what I'm missing.


XenForo developer
Staff member
There's nothing in the code that would apply date limits or anything like that to the ability to like a post. I could only guess that perhaps an add-on is interfering, so please confirm the issue with all add-ons disabled. If simply disabling the add-ons doesn't resolve it, please then go to <url>/install/ and choose the option to rebuild the master data to see if that helps.