Apart from what results/recommendations DavidR provided you with, and what you should take up with a knowledgable website admin and/or website developer or your hoster, you have the following issues that should be tackled a.s.a.p.
Update your version of Word Press CMS, as it is outdated. A check of threat intelligence sources and blacklists was performed against the hostname and IP address of the target.
The findings will identify reputation issues or even the presence of malicious code.
DShield CLEAN
AlienVault OTX CLEAN
Cisco Talos CLEAN
abuse.ch (Feodo) CLEAN
URLhaus CLEAN
Retirable jQuery library (also mentioned in DavidR's oversight in another fashion, but similarly denoting weaknesses):
https://retire.insecurity.today/#!/scan/7531164b1d83599113babe89bb31bcf5a7a5766d37ecdb467ef2e4659f7fbb9fSpamhaus (Drop / eDrop) CLEAN
Idem:
See F-Grade scan results here:
https://observatory.mozilla.org/analyze/lectuepubgratis.com (non-compliant TLS results) (no HSTS)
Site was flagged probably because of IP alerts like:
https://www.abuseipdb.com/check/104.27.172.27polonus (volunteer 3rd party cold recon website security-analyst and website error-hunter)