[tor-relays] Install on Tor on fresh Debian 10 failed (gpg key invalid)

Hello!

I updated my VPS with a fresh Debian 10 install. According procedure in the documentation

'curl https://deb.torproject.org/torproject.org/A3C4F0F979CAA22CDBA8F512EE8CBC9E88... | gpg --import'

I get the error message '2019-10-17 20:34:32 (1.01 MB/s) - ‘A3C4F0F979CAA22CDBA8F512EE8CBC9E886DDD89.asc’ saved [19665/19665] gpg: no valid OpenPGP data found. gpg: Total number processed: 0

What is going wrong? Is this an invalid key? After weeks ago my other install on Debian 10 was ok.

Best regards! Olaf