Hi,
I have one MPE and one APE
Which licenses I need purchase to make HA for both (MPE + APE)?
2 HA licenses, one per server. (IF you want both of them to be HA)
Do I need buy licenses on secondary MPE and APE?
You only need to buy the High Availability license (1 for each server).
The specific license is:
SolarWinds High Availability for SolarWinds Orion - License with 1st-Year Maintenance
HA works as an active/passive pair with HA pools. So if you want to provide HA for both servers, you need 2 pools hence 2 HA licenses.