We recommend that any whitelisting you have in place should use the URL and not the IP address so that any future IP address changes will not affect you. If you have whitelisted this IP for any specific reason then please update as highlighted above to ensure the product continues to function as expected.
You can confirm if your on-premises version is syncing correctly by running below SQL command on the database server:
select max(vuln_modified_date) from vuln_track.vuln;
The output should be the most recent date when the database was updated. Typically it should be the same working date when the query was run. If the date is or lower than 2019-05-24 then it is possible that the vuln_track database is not updating correctly.
In some corporate environments, the DNS entries are cached at the proxy level. If the date above is or lesser than 2019-05-24, please ensure your IT infrastructure is not caching the old IP address.
You can also use the command "nslookup sync.secunia.com" on the SVM server and the output should be similar as below: