You can try refreshing it. If not, you can check the WeChat health code. Just open WeChat on your mobile phone first, then click Me in the lower right corner, select Pay, click Enter, then slide down to find the epidemic prevention health code, then click View Epidemic Prevention Health Code, select Get it now, then log in for verification, and finally fill in the information and submit it.
You can also search for XXX's health code, register, or view it in WeChat applet.