Seeing that so many people have encountered this problem, I will reply to everyone and provide a solution. The test is effective:
1. Make sure that SSL is turned on and available for your domain name.
This can be confirmed with your service provider.
2.Clear mysql cache through phpMyAdmin
TRUNCATE `ps_smarty_cache`
TRUNCATE `ps_smarty_lazy_cache`
3. Turn on SSL
CONFIGURE ---> Shop Parameters ---> General ---> Preferences
- Enable SSL:YES
- Enable SSL on all pages:YES
Don't forget to save the settings, I wish you success, I have successfully turned on SSL.
Merry Christmas everyone~