I am having the same problem. The thing is that my Power BI Gateway is updating just fine.
But when I try to connect with my Power BI Desktop do my IBM DB2 I get this message: Microsoft Db2 Client: The request for the host resource failed. SQLSTATE=HY000 SQLCODE=-357
I could connect regullarly few days ago. Nothing has chaneged on my Database.
It started working again after February 2019 Powe BI Desktop Upgrade. Now my Gateway can't connect to my IBM DB2. I wonder if Microsoft will manage to correct this on next Gateway update.