Fibaro Double Switch 2 error when trying to include

k1s

I often get this when trying to include a Fibaro Double Switch 2:

vdevice.drivers.zwavebasic.pair.TRANSMIT_COMPLETE_ACK_UNKNOWN

Can somebody tell me what the error means please

(More often it just fails to find the device or goes through the inclusion dialogue but the device doesnt appear, then when I try to add it again, it says it's already paired, but isn't in the list.  When I go remove z-wave devices in settings it seems to remove ebery time.  So far in 5 hours, I have successully added 1 of my 18 Fibaro Double Switch 2 devices....losing the will here)

Oy1974

Do you try to include them close at homey??

Otherwise bring them close to homey or bring homey to them

k1s

Yes, extension leads, for Homey and Wifi access point so Homey is 1.5 metres away