iMessage not activating on iPhone after reboot

After rebooting iOS 26 on my Iphone 17, activation lock was activated. After logging in, everything worked as usual, but iMessage broke. When I try to turn it on, an error appears. SMS messages for activation are sometimes sent, but iMessage still doesn't work, and in most cases, an activation error simply appears. In the iCloud settings, it says my phone number can't be used for iMessage because it requires a SIM card linked to an Apple device. Previously, everything worked fine with the same SIM card on the same device. Restarting, disabling Wi-Fi, updating to the latest iOS version, resetting network settings, using airplane mode, signing out of iCloud, and changing time zones all help. Trying to activate through the website hasn't worked, even though several days have passed.