There's a known issue in iOS 13/iPadOS 13 and later that prevents users from using AirDrop or other share options such as email to share their files with other devices and apps.
Symptoms
In reported cases, the Save This File window is blank and doesn't display any sharing options. This may prevent you from sharing your Shapr3D projects.
Workaround
Try any of the following workarounds to help solve the issue:
Reset networksettings: Go to Settings > General > Transfer or Reset iPad > Reset > Reset Network Settings.