Trouble connecting zwave devices

I am using a Smartthings mesh wifi with the hub portion turned on and I can’t connect any zwave devices unless they are practically touching the router/hub. I had installed a Leviton dimmer switch and it worked when the hub was next to the switch. Once the hub was back at its home approximately 40’ away it wont connect. I bought a range extender thinking that could be the issue. Again I could only connect if they were practically touching and once they were apart 20-30’ it wouldn’t connect.I have a zigbee outlet switch that connected right away and works great, about 20’ away. Any ideas or do I need to get Samsung tech support involved?

Do you have any cordless telephones, usb 3.0 cords or other wireless devices/network equipment that may be causing interference where the hub is located?

no phones. normal wifi devices like phones laptop Echo etc. nothing i know of between hub and devices

How many walls are between the hub and switch? Do you have any z wave repeaters?

No walls. I have a repeater but it won’t stay connected when i move the hub back to its normal place. Less than 30’ away