I think it can happen if the page is very light on the HTML aspect and doing too much in the JS, so the page 'appears' empty to the crawler. Their crawler is p

I think it can happen if the page is very light on the HTML aspect and doing too much in the JS, so the page 'appears' empty to the crawler. Their crawler is perfectly fine with SPAs, and I've indexed SPAs before. But when I visited your URL it seems to be doing too much before gets to the actual content. Notably I see an initial batch of JS loads, a pause, and then another batch of JS loads before the actual content finally appears - there must be some threshold that the crawler is hitting to make it say that's a soft 404. When visiting your page, I see almost 400 requests over 8MB, can that be reduced, can you load your content quickly instead of this initial setup you're doing?