We are experiencing the same problem as many other users in here. When testing the robot.txt Google should be allowed to crawl, but is still giving us the "URL blocked by robot.txt" error inside Search Console.
We also had a developer do a custom auto-geo currency selector. Is that really what is causing the problem?? The crawling issues came little by little in the time after implementation, cf. screen dump bellow. Please HELP us Shopify! :-)