Your QR code opens a website link I suppose? It could be that the website / IP / Server IP range in your QR code has been 'red flagged' and blocked inside China. In such a case such links won't open for China mainland viewers.
It could also be your website link has been blocked by some ISPs in China. I know this because we serve several foreign sites that open to some users in China while others on some ISPs have the site blocked. There are still ISP blocks within China. You would need to physically be here and test it with connected devices different ISPs to really know. Also if the site does not have a China ICP license and is trying to sell a service or product to Chinese mainland audience. It's up to the Chinese ISPs to decide if they block your link or not. They have teams online for this ;)