Widget URLs incorrect

I’m having an issue with the widget, whereby the URLs for each download isn’t rendering correctly.

For example, the link to a file will be like:

https://my-wp-site.com/?post_type=dlm_download&p=75/download-info/name-of-my-file/

When any such link is clicked, I get a 404 error.

I’ve removed all custom functions in my theme but the problem remains, although if I revert back to the standard WordPress theme, the widget works fine.

I just can’t work out what in my theme is causing the widget to behave this way, and my deadline for completion is nearing!

Thanks to anyone that might be able to shed any light on this.

Bets regards,

Matt