Hello,
I’m sorry that you’re running into this issue, but I’ll be happy to help you figure out what’s going on!
I took a look at the page, but the next/previous links appear to be working correctly on my end – were you able to get this resolved?
If not, I would first recommend flushing the permalinks by going to Settings > Permalinks and clicking “Save”. If this doesn’t make a difference, the next step would be to run through the steps outlined here to check for any conflicts that might be occurring between your theme and other plugins.
Please let me know what you find!
Thanks,
Jennifer