Sites using third party shipping apps like ShipIt and Fastway/AP Shipping may be experiencing problems with no shipping rates being loaded at checkout.
If your shipping rates are set up through admin/shipping you are not affected.
We've raised it to Shopify, and they've published a status alert. It looks like it is almost fixed (1pm EST 31 May 2018).
Cloudflare outage is affecting access to SOME Shopify Sites from Some locations.At approx. 5pm on 21/6/22 there was a Cloudflare outage. Cloudflare provides a performance/security layer for Shopify and many other websites.
UPDATE: here is Cloudflare’s incident report: