Seiko Smart Label Printer

Test the Label Printer connected directly to the iMac using a USB-A to USB-C adapter.

for a few examples,

USB-C to USB Adapter - Apple

https://www.amazon.com/dp/B07VP4R8P5/ref=sspa_dk_detail_1?

https://www.amazon.com/dp/B0B9N3QSL3/ref=sspa_dk_detail_3?

https://www.target.com/p/philips-usb-c-to-3-0-usb-a-female-adapter/-/A-79804275

You're welcome.

Does that iVanky Dock have an external power source?

If not, then it may not provide enough power for more than one bus powered external drive and a couple of other devices.

Then it should have no problem handling a couple of bus powered drives and other devices.