Missing June data in Search Console is a Google bug
Two well known SEOs saw the same gap in the same report on the same morning, so it is not your site.
Google Search Console (Google's free tool that shows how your site is doing in search) is showing missing data this week. The Page Indexing report, which lists the pages Google has stored and can show in results, is missing a large chunk of data from June.
Who spotted it
Barry Schwartz first reported the missing June data in the Page Indexing report. Glenn Gabe confirmed he saw the same gap, and said the data had been there earlier. Separately, Marie Haynes said Search Console was glitchy that same morning because its Performance report, which shows clicks and positions, was getting stuck on a loading wheel for some people, a different problem in a different report.
What Google said
Barry Schwartz later posted that Google's @johnmu responded about the page indexing data loss and that his story was updated. The tweet itself does not say what Google's answer was, so we do not know yet whether the June data is coming back or gone for good.
What this means for your site
A hole in a Search Console chart looks alarming. It reads like Google suddenly dropped your pages. In this case it looks like a reporting problem on Google's end, not a change to how your site is indexed or ranked, since two separate people who watch these reports closely saw the same gap on the same morning.
If your Performance report will not load, Marie Haynes gave a workaround. Click into another report, such as Page Indexing, then go back to the Performance report and it should work.
Do not act on the missing June numbers. Do not delete pages, do not rewrite anything, and do not request reindexing because of a dip that only exists in the chart. Your actual traffic is the better check right now. Open your own analytics and see whether real visits changed in June. If they did not, nothing happened to your site.
Super-new bug in GSC. Page indexing reporting. A large chunk of data is missing this morning. It was there yesterday (or even earlier today).
If you are getting this spinning wheel, you can just click on another report - like Page Indexing and then go back to the Search Performance report and it will work.