Media Library shows no images when attempting to add to, or create, a gallery

I’m attempting to create a new post, but when I go to create a gallery of images, it spins for a second, then says there are no images available. I have experienced this in the past, but was able to work around by selecting a specific month. That’s not working here, whether the images are newly added, or old. I have tried switching browsers, empty caches, cookies, & all that, and have made sure everything is up to date. As far as I am aware, I don’t have any plug-ins that would cause the problem. I only use an image optimizer and have never had trouble before. Nothing has changed since I was able to successfully add images to a gallery, so what do I do now? Using WordPress 5.4.1 hosted on Siteground

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