GnuTLS error -15

[vespasian]

I'm trying to get an ftp server setup on a google cloud virtual machine.
I followed these instructions precisely:
https://www.siteyaar.com/setup-ftp-serv ... ogle-cloud
But filezilla gives me this error:

Error: GnuTLS error -15 in gnutls_record_recv: An unexpected TLS packet was received.
Error: Could not read from socket: ECONNABORTED - Connection aborted
Error: Could not connect to server

I tried disabling TLS by commenting out these lines and bouncing the ftp server, but I still get the error:
# ssl_tlsv1=YES
# ssl_sslv2=NO
# ssl_sslv3=NO

[botg]

Please post a complete and unmodified log of a connection attempt.