SPF or DKIM Bounce back errors

We are constantly getting this error now. Can someone please help!!

heiwireless.com

host gmail-smtp-in.l.google.com [142.250.102.27]

    SMTP error from remote mail server after pipelined end of data:

    550-5.7.26 This mail is unauthenticated, which poses a security risk to the

    550-5.7.26 sender and Gmail users, and has been blocked. The sender must

    550-5.7.26 authenticate with at least one of SPF or DKIM. For this message,

    550-5.7.26 DKIM checks did not pass and SPF check for [heiwireless.com] did not

    550-5.7.26 pass with ip: [66.96.188.4]. The sender should visit

    550-5.7.26  https://support.google.com/mail/answer/81126#authentication for

    550 5.7.26 instructions on setting up authentication. b1-20020a05640202c100b0050d1e0b3e2esi2992921edx.614 - gsmtp