Thanks a lot for you help. Yes, the public Sucuri site shows the scan error but I have the premium account monitoring the site 24/7 and it shows no issues at all even at server side as you can see in the printscreen in attach. I´m also using Wordfence as firewall and all the scans show no warnings.
Honestly I believe it´s a false positive since, beside Avast, no more sites/software blacklisted our domain, including McAfee or Norton. Hope I can get some feedback from Avast soon because the blocking/virus warning is really damaging my business and brand reputation.