If all apps stopped opening at once, Apple has most likely revoked the certificate. It is not your fault and nothing is broken. If only one app does not open, the cause is the app itself or Developer Mode.
What to do
Check Developer Mode. It sometimes turns off after an iOS update: Settings → Privacy & Security → Developer Mode.
Check the certificate. If it was revoked within the warranty period, we replace it for free.
Reinstall over the top. Tap Install again without deleting the app — your data and progress are kept.
Still not working?
Certificate revoked or nothing helped — message us and we will replace it under the warranty.