Signature is not saved

and_rew69 wrote:

Signature is not saved in the mail.

The built-in Mail application does not save signatures for all accounts. Having created a signature, it will work until the device or application reboots.

I need a signature! How to fix the problem?

Verify from All Signatures, that you manually drag & drop with your pointer, to the appropriate mail account.

Create and use email signatures in Mail on Mac - Apple Support

I did too. But I lose every time my signatures after rebooting.