When operating on battery power and the battery level drops below ~20% on a MacBook Pro or MacBook Air, macOS will decrease 10/25G Ethernet transmit performance in order to conserve battery life for the laptop. This also occurs when macOS Low Power Mode is active.
In some rare circumstances, the Solo10G will not function connected to a particular Thunderbolt port. Try plugging into a different Thunderbolt port on the computer. For example, you must plug into the furthest back Thunderbolt port in an HB Z Book Studio G5.