I seem to only be able to AirDrop to/from one of my Apple devices to another if one of them is signed out of iCloud. I have all my devices (iPhone X, 2017 iMac High Sierra, 2017 MacBook Air High Sierra) all signed in to my iCloud account (the same account). The devices cannot see each other in AirDrop unless I sign one of them out of iCloud.
For example, if I sign my MacBook Air out of iCloud, then my MacBook Air shows in my iMac's AirDrop and I can freely transfer files to it. Once I sign back into iCloud, it goes away.
Note: I can see and AirDrop to any of my colleagues' devices just fine across all of my devices. I just can't send to any of my own devices unless I sign out of iCloud.
I've tried all of the standard AirDrop troubleshooting (Making sure Bluetooth is on, same Wifi, update all devices, restart, etc).