GA4 funnel exploration won’t display known data

I am using a funnel exploration in GA4 to map customer journeys from Google Search Ads through my company’s e-commerce site. The funnel begins with "session_start" and ends with "purchase," and there are several custom events in between.

A few weeks ago, the funnel stopped displaying any data for the "Paid Traffic" segment, and gave the message "No data for this combination of segments, values, filters, and date range."

I know from the Search Console that we are getting clicks on our ad, and I know that GA4 is recording the events on our site, because I can see them in the path exploration. However, looking at the same segment over the same date range in the funnel exploration gives the error above. I changed the funnel to just display the number of users that started a session on our site, and am still getting a message that there is no data. I have attached screenshots of the path exploration as well as the abbreviated funnel.

path_exploration empty_funnel

I’m wondering if anyone would have any insight into why the funnel would have stopped populating. I have posted on the Google Analytics Help forum with no success, and Google doesn’t seem to have much in the way of support for GA4. I have tried expanding the date range from what is shown in the screenshots to include more data, with similar results. Any help would be greatly appreciated!