Several iPod touch, iPad and iPhone users reported the following error message when attempting to access the iTunes Store, App Store, the Mail app, or a website: The certificate for this server is invalid. You might also see the error cannot verify server identity.
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Quick tips 
Follow these quick tips when getting certificate errors on your iPhone, iPad, or iPod
- Restart your device
- Force close the app and launch it again
- Update your device’s Date & Time settings to Set Automatically
- For issues with the Mail app, delete the account and add it back
- Reset all settings on your device
What is a certificate?
A secure website that encrypts data needs to obtain a site or host certificate from a trusted certification authority (CA) to verify that the site is indeed secure. These security certificates are part of the HTTPS (HyperText Transfer Protocol Secure) protocol, designed to encrypt all data that travels back and forth between a server and a user’s browser.
Basically, a certificate ensures that your data is indeed encrypted so any information you provide is kept private.
These errors indicate that a website or server is not trustworthy, so never enter any private, confidential, or sensitive personal information if you see these types of certificate errors.
What are certificate errors like the certificate for this server is invalid?
You find certificate errors when there’s an issue with a site’s or server’s use of a certificate.
One of the most common reasons for certificate errors is when your device’s or computer’s date & time are incorrect
Luckily, this is an easy fix.
Check your iPad, iPhone or iPod touch’s date and time by going to Settings > General > Date & Time. we recommend toggling on Set Automatically instead of entering manually.
For Macs, go to System Preferences > Date & Time and tick the box for Set date and time automatically. 
Wait it out and visit site or app later
If you continue to see the error after updating the date & time, it’s possible the certificate has expired and needs renewal.
Do not continue with the site until the certificate warning is gone.
Since this is a problem with the server or website, there is nothing you can do other than wait for the certificate to renew.
Toggle off or reset Safari’s Fraudulent Website Warning
If you’re confident that the site is secure or it’s your own site/blog, you can toggle off Safari’s warnings.
When you turn on Fraudulent Website Warning, Safari displays a warning if a site is suspected of phishing or other fraudulent behavior. When browsing with this feature on, Safari might verify the site address with Google Safe Browsing to ensure it’s not fraudulent.
While we don’t recommend it, you can disable Fraudulent Website Warnings in Safari by going to Settings > Safari, then toggling the Fraudulent Website Warning off. 
A better option is to reset it!
- On your device, go to Settings > Safari > toggle off the Fraudulent Website Warning
- Restart your device
- Return to those same settings and toggle the Fraudulent Website Warning back on
- Test the site or app again
Seeing this certificate for this server is invalid error on a Mac?
Check if a certificate is valid using Keychain Access
Use your Mac’s Certificate Assistant in Keychain Access to evaluate a certificate by looking at its trust policy and determine if it is valid.
- Open Keychain Access from your Mac’s Applications > Utilities folder
- Choose Certificates in the Category list
- Double-click the certificate you wish to evaluate
- Go to the top menu and choose Keychain Access > Certificate Assistant > Evaluate certificate name
- Select a trust policy
- Click Continue
Reader tips 
- For email account issues, go to Settings> Passwords & Accounts> tap the specific email account > Advanced > toggle off Use SSL
Obsessed with tech since the early arrival of A/UX on Apple, Sudz (SK) is responsible for the editorial direction of AppleToolBox. He is based out of Los Angeles, CA.
Sudz specializes in covering all things macOS, having reviewed dozens of OS X and macOS developments over the years.
In a former life, Sudz worked helping Fortune 100 companies with their technology and business transformation aspirations.
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My defender app says this on all my devices tried the time thing on all of them but didn’t fix it any other way to fix it
thanks alot ma problem was solved through u. appreciate
The date, time and timezone are all correct on my phone, but this message persists whenever I tried to connect with iCloud.
Thank you very much you help me
Excellent fix thanks worked
Thanks. It solved mynproblem. However i needed to set up the time manually.
It is happening on my ipad whilst using itunes. The time zone is set up correctly
Dude Thanks You So Much I Have This Problem For Maybe 2 Months Ago ..
Finally I Got A Solution Thanks Dude
Same problem for me with my IPad. If I change to set automatically the Time zone box goes into perpetual timeout. Usual frustration, I guess the idea is to make us all expect that nothing works as it should then we are grateful for the time it does work.
Same here. Date/time is correct but still receive the certificate error.
Get the same prob with my date and time are both correct, tried to ON the set automatically but the prob still dont go away.
What if you get this error and all your date, time, and timezone settings are correct?