iTunes Enterprise 12.6.5.3 Fails to download apps

After experiencing the same issue on multiple machines with the same operating system and iTunes versions i spoke with an experienced Apple Enterprise Support team member. They provided a solution with seems the be simplicity itself after two days of careful consultation and screen sharing. By the way, they couldn't reproduce the problem from their end, hence the feeling the the account file itself might be the culprit. It is not an app version blocking issue per-se, more an iTunes/Apple Account security 'feature'. If your account details or payment methods have been flagged for 'non-authorised activity' or 'suspicious transactions' it maybe suspended (without notification or human intervention) until such times as your ID is re-established and the flag removed. Sometimes this flagging can occur well after the said suspicious event (weeks, months). I my case i had multiple Apple accounts in several countries. Only one of which had the 'update error 8288' issue. This one account had been not been flagged as needing ID verification strangely. After changing the account payment method to "NONE' and then re-entering the required credit card details, the Enterprise rep verified my ID using the 3 questions set when the account was first created. Violå. Problem solved in this instance. All updates completed successfully and all machines. The Mac operating version or iTunes version was not really the issue in my case.