The solution of "Novice Tutorial" about "expired mobile phone certificate" leading to the inability to install software! When installing software, there are often some "certificate X X" problems, which make it impossible to install software. Now summarize the possible problems! The first thing to note is that the certificate is valid. The certificate can be installed whether it is within the validity period or not. What needs to be done is to adjust the time of the mobile phone when installing. Then, in Settings-Phone Settings-Applications-Program Management, make sure that "Software Installation" is "All" and "Online Certificate Check" is "Off". 1. Certificate error The prompt of certificate error is the most common. Cause of the problem (1) Self-signed programs need to be installed without signature, (2) software signed by others with private certificates (that is, certificates that provide serial number applications), and (3) software that has been signed repeatedly (that is, it has been signed once and again). Solution: (1) sign and install, (2) download unsigned software and sign it yourself, (3) install with software without repeated signature. Find someone without a certificate to do it. 2. The problem of certificate restriction is not very common, but it is still annoying. The reason is that both the certificate and the signature need a key. Some signature software will prompt when the keys do not match, but others will continue to sign, so that the signature software will prompt the certificate restriction when installing. Another reason is that the certificate file was damaged during transmission. Solution: First try to replace the key file. You'd better ask the person who helped you to make the certificate to send you his key file. If it still can't be solved, you can reissue a new certificate. 3. The certificate has expired and is invalid. Each certificate has a validity period. Only those within the validity period can be installed. Double-click the computer to open the certificate to check the validity period. However, the signed software can't look at the validity period, so it can only be tried when it is installed. Solution: Just change the time of the mobile phone. Generally, the normal date will be adjusted first, then adjusted in three months, and the installation will be adjusted once to see the error. The expiration of the certificate means that the current mobile phone time is after the validity period of the certificate and can be adjusted forward. If the certificate is invalid, it will be revoked. The mobile phone time is before the validity period of the certificate, so this time should be adjusted backwards (in fact, this error prompt will not appear if it is adjusted to the correct date). Free: The solution to the problem is 1. First look at whether the software you installed needs to be signed, and all the software that doesn't need to be signed has already been signed. Look at the file name suffix before signing. sisx。 You don't need to sign. Sister only needs to sign, but not all. Sis file needs to be signed. Generally, those who need to sign will be explained when downloading. 2. Check whether the certificate was successfully signed and the software was installed before. The certificate has been successfully signed and installed, which means that the certificate is valid. You can skip 4. 3. Try signing another software, and don't lock a software. If other software can be signed and installed, it can be explained that there is something wrong with the original installation program and it can be downloaded again. 4. According to the error prompt, choose whether to replace the key file or make a new certificate. These basic steps can solve more than 80% of the problems. If you cannot install them, please ask for help again.