Hi Jurgen,
I'm assuming LACP with SN2700 vs. a hyperv doesn't work in your setup and not as a general statement.
1. can you please provide the SN2700 software version: "show version"
2. output of show-running config -> also specifiy which ports are connected to the Hyper-V
3. output of "show lacp counters"
4. output of "show lacp interfaces ethernet 1/X neighbor" (when X is the port that is part of the port-channel), need to run the same command for each port which is part of the same port-channel which isn't working.
5. output of "show lacp interfaces ethernet 1/x"