I just created an absolutely new clean install of Joomla 3.4 then updated it to Joomla 3.4.5. I then installed Zap Calendar Pro 4.2.1 on it, absolutely nothing else, and the filter module does not properly install. The Extension manager shows a X in it's status column for this module.

I don't think you should not need access to my site to reproduce this issue.

I have the same error on a new install. Is there a workaround?

zapcalendar 4.14 did load though. I am using this until 4.2.1 is fixed.

Version 4.14 does not work with the latest clean install of joomla. Version 4.2.0 and 4.2.1 does not install any plugins. I am using v4.2.1 lite to get anything working. I am missing a lot of functionality. I have tried on two different systems and have this same problem.

I don't desire to downgrade joomla but will if needed. Any suggestions?

I have fixed this problem on my two systems. I forced an update of Joomla by manually installing the current stable version from www.joomla.org/download.html and downloading v3.4.5. I used the "manage extensions, install" and voila, it worked.

As a minor issue, weblinks then created an error and loaded two instances. I uninstalled both instances and then installed the latest weblinks. This is not the first I have seen on problems for weblinks and I may trash it as I find it creates more troubles than it is worth, at least in my opinion.

After these steps Zapcalendar Pro installed as expected.