What are the reasons for invalid SSL certificates

There are many things about invalid SSL certificates. Why are there so many invalid SSL certificates? There may be the following reasons.
1. The virtual host is configured incorrectly.
A common configuration error is to make these plaintext websites and other websites that use encryption on port 433 use the same address. This way, if users try to use the https plaintext protocol to access the website, an error will occur: integration The prime and domain names do not match.
2. Insufficient domain name coverage.
In a few cases, the website administrator purchases and deploys an SSL certificate, but the SSL certificate does not contain all the website domain names. If the website has other domain names, the certificate also needs to include other domain names.
3. Self-signed SSL certificate and private CA.
Self-signed SSL certificates and private CAs are not suitable for public use. Because this type of certificate cannot be easily distinguished from the middleman. According to the editor, almost half of the invalid certificate group is due to this reason. Many people use this type of certificate for several reasons: purchase, configuration, and renewal bring some troublesome work, and it also requires continuous investment; think that the certificate should be free, and refuse to pay for it.
4. The SSL certificate has expired.
Some people did not notice the expiration time of the SSL certificate when using it, or the webmaster forgot to renew the visa certificate or gave up obtaining a valid certificate instead of taking the expired certificate offline. The editor recommends Anxin certificate promoters. Because after the Anxin certificate promoter purchases an SSL certificate, you don't have to worry about not knowing when the SSL certificate expires. Anxin certificate customer service will remind you that the SSL certificate is about to expire.
5. The certificate used by the device.
Many devices are web-based management interfaces, these interfaces will require the use of secure communication. When these devices are manufactured, the domain name and IP are still uncertain, which means that the manufacturer cannot install a valid certificate.