Check the value of this status:

Discovered - currently not indexed: The page was found by Google, but not crawled yet. Typically, Google wanted to crawl the URL but this was expected to overload the site; therefore Google rescheduled the crawl. This is why the last crawl date is empty on the report.

It is likely that your website is performing poorly and this, in turn, has a negative effect on Google's crawling budget:

The crawl rate can go up and down based on a couple of factors:

Crawl health: if the site responds really quickly for a while, the limit goes up, meaning more connections can be used to crawl. If the site slows down or responds with server errors, the limit goes down and Googlebot crawls less.

Check the performance of your website on a Google tester and, if required, optimize to a green result.