Took delivery of a new iPad last week, "upgraded" to IOS11.2 on the day of purchase and , yes, the Push feature is also not functioning. All I could do was to open the Mail app and manually refresh. I have tried all the proposed solutions put forward on this forum but to no avail.
The only work around, which I found is :
1. Settings > Accounts & Passwords > Fetch New Data. Disable "Push". Then switch every email account, including iCloud, to "Fetch". Finally, I switched the "Fetch" setting to every 15 minutes.
2. Settings > Mail> Notifications > Enable " Allow Notifications"> Email Account > Alerts > Enable "Show on Lock Screen" > Enable "Show as Banners".
I now receive new emails automatically every 15 minutes via temporary banner alerts on the iPad, which is a vast improvement on manually retrieving emails. It's still not "Push" but I can live with this until Apple finds a solution.
IOS 11 has not been one of their finest moments.