Hello David,
I see now you are in the US, aren’t you? There is the FIFO violation if you trade with many EAs with same lots. It is not like you are breaking the rules or something, this is just how US brokers work.
Basically you are not able to trade more than one Expert Advisor for one currency pair in one account. The rule stands exactly as they wrote to you, that you should close first your older trade.
There are many traders in the US complaining about this FIFO violation rule, but that comes from the regulations in the country, and the legit brokers must follow it. I am not really the man who will comment it if they decided that this is good, then it is :)
Kind regards,