[SmartCrawl] Unable to run SEO Checkup

SEO Checkup persistently claims:
“There was an error crawling http://www.domain.com/, we weren’t able to get meaningful results”

Also, we’re seeing this message at the top of every admin screen even though Yoast SEO (free) has been deactivated & deleted:
“We’ve detected you have Yoast SEO settings. Do you want to auto-import your configuration into SmartCrawl?”

We tried reinstalling SmartCrawl, even reinstalled Yoast and imported its settings to see if that helped, but both issues persist even after that.