The Prior version of Infuse for iOS had no trouble identifying My DS server from Synology. Ver 2.2.1 no longer sees the NAS but I am able to connect to it manually and everything operates properly.
Did you remove the previously saved share, or are you just trying to set it up again?
Once a share has been setup/saved in Infuse, it will be listed under the Saved Shares list, and will be hidden from the Available Shares list.