What it means
Unlike a local setting, 'AutoTrading disabled by server' is set on the broker's side. Even with AutoTrading on and your EA enabled, the server is refusing automated orders on that account. Your manual trading may still work.
Common causes
The account type does not permit EAs (some accounts block algorithmic trading). Automated trading is temporarily disabled during maintenance or over the weekend. The broker restricts EAs on certain symbols or in certain conditions. Or a compliance setting on your specific account.
Step-by-step fix
First rule out the local causes — confirm AutoTrading is green and live trading is enabled — so you know it really is the server. Then check whether the market and automated trading are simply closed for the weekend. If it persists during open hours, contact the broker and ask whether EAs are allowed on your account type and, if not, whether an account that permits them is available.
How to prevent it
Before relying on an EA, confirm with the broker that your account type supports automated trading. Read the account terms. Choose a broker and account that explicitly allow EAs if that is central to how you trade.
Broker's fault or yours?
This is a broker-side setting, so the cause is on their end — but it is often a legitimate account policy rather than a fault. The real question is whether their policy fits your needs; if EAs are essential to you, pick a broker that supports them.