Nordic ble is unable to send data to the host computer

[Lappland]

Sending array unit8 type data using BLE failed, and attempting to take 2 bytes of data from the array and send it also failed. Does anyone know what this log error means? How to solve it?

[Vidar Berg]

bt_nus_send() will return -EINVAL (-22) if the client (host) is not subscribed to notifications from this characteristic.