Issue for delivering Gmail with second domain

Hello all,
i have set up a second domain and when i try to send an email to gmail from the second domain i got this error:

Undelivered Mail Returned to Sender

host[ww.xx.yyy.zz] said:
550-5.7.26 This mail has been blocked because the sender is
unauthenticated. 550-5.7.26 Gmail requires all senders to authenticate with
either SPF or DKIM. 550-5.7.26 550-5.7.26 Authentication results:
550-5.7.26 DKIM = did not pass 550-5.7.26 SPF [second.domain] with ip:
[ww.xx.yyy.zz] = did not pass 550-5.7.26 550-5.7.26 To mitigate this
issue, please visit Gmail’s authentication guide 550-5.7.26 for
instructions on setting up authentication: 550 5.7.26
i can deliver to some other email adresses but fail with Gmail.
please can you help me figure out.
Thanks in advance

Did you force ssl cert for that domain and potentially wait like 24 hours for dns propagation to work?

Are you using external DNS or using the MiaB server to handle DNS?

i am using MiaB server to handle DNS ; i have set ns1 and ns2 to point to from the DNS page