Windows Server 2016 Hyper-V “password is not correct” to Synology share

I could not get Windows Server 2016 Hyper-V (10.0.14393) in a WORKGROUP to authenticate to Synology SMB share if the Synology unit (DSM 6.1.3-15152) is set to maximum SMB version 3.  I kept getting error: “System error 86 has occurred. The specified network password is not correct.” (86 == ERROR_INVALID_PASSWORD), on the Hyper-V system.  I retried typing the username and password, many times, all with the same error even though I knew the username and password were okay because I could use the same share from a Windows 7 and a Windows 10 machine. I never saw any errors in Synology’s log or in Windows event viewer about this.

I had to go back to SMB 2.0 on Synology– in DSM, Control panel > File Services > SMB > Advanced Settings > “Maximum SMB” set to SMB2.  Then Windows Server 2016 Hyper-V Core would connect to the Synology share.