Hey Mark,
I’m sorry to hear about these issues. When I try searching or paging through the Previous/Next months on my own site, things work fine, so we’ll need to do some digging here to figure out the exact culprit on your site.
1. Can you share your “System Information” with us? Here’s how to do that → https://theeventscalendar.com/knowledgebase/sharing-sys-info/
2. It looks like you might have made some customizations on your site. Can you confirm whether or not there are customizations to the calendar on your site?
3. I see that your Events Calendar Pro license expired in September 2015. This could mean that your current versions of the software are outdated. We cannot support outdated versions of our plugins, and so the first order of business before any further support can be done here would be to update your versions of our plugins to their most recent versions:
• The Events Calendar: 4.1.0.1
• Events Calendar Pro: 4.1
Thank you!
George