For me, Continuity's universal clipboard functionality has always been a bit uneven, but with newer hardware, it has become a little more reliable.
The problem is to make it work steadily. I've read the Apple support document, use the universal clipboard to copy-and-paste between your Apple devices, which is sadly simplistic.
Yes, Bluetooth, Wi-Fi and Transfer are enabled and all my devices are properly connected to the same iCloud account. The other features of Continuity (Handoff, in particular) seem to work well.
However, what I regularly experience between my iPad Pro 11 "and my iPhone XS is: When I try to copy to one device and paste it on another, it will not work. at all For the first time, then if I repeat the collage, the device I'm sticking to will display a "Paste of …" alert, I'll have to wait about 5 seconds, then the text will be pasted correctly.
Previously, I saw this message appear when you paste a fairly large text (a page, for example), but now it repeats itself even when I stick only a few words. This is however do not the case between iOS devices and my MacBook Pro 2018 under macOS Mojave 10.14.5.
I've already posted about it – with different material (older):
Previously, the most trusted fix for Universal Clipboard did not work at all – as noted on multiple sites – was to disconnect all devices from the iCloud account, reboot, and reconnect to iCloud on all devices. However, as noted above, Universal Clipboard works to some extent for me, although disconnecting from iCloud and reconnecting is not as easy as it seems – many parameters need to be reestablished.
Is this kind of problem comparable to the course with Universal Clipboard? or is there a clear way to make it work quickly and reliably? All my devices use the latest versions of the system software (macOS Mojave 10.14.5 and iOS 12.13.1).