I get a lot of times error with 2 sites. Most of times I get an internal error, after reloading .htaccess and saving the permalinks the problem is solved for a couple of days, and now one site is not showing no products anymore in the shop.
In de private section I give you more information.
I check one of your sites and could access without issues. I also noticed that PHP Max Input Vars parameter need to increase 10000 or higher in your PHP configuration and import the demo again.
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