Some errors may happen. Here you can read some advice which can help you resolve such errors.

Sending from Cyclone 3DR to Autocad

Couldn't find Cyclone 3DR add-in 19.1.5.24477 (19.1.4.24386 found instead) means Cyclone 3DR and Autocad Add-in are not compatible. The Autocad Add-in is installed automatically: each Cyclone 3DR installation replaces the previous add-in. Thus, you have to work with the last Cyclone 3DR version installed on your computer.

Couldn't find a compatible AutoCAD application. Try 3DRCHOOSEVERSION inside AutoCAD or see the help means:

You forgot to open Autocad,
or Cyclone 3DR tries to connect to the last instance of Autocad application launched which was closed. Open again Autocad,
or you are not using the same major version on Cyclone 3DR and Autocad Add-in. For instance, you are using Cyclone 3DR 18.1 and you have just installed Cyclone 3DR 19.1; you can switch between major version by typing 3DRCHOOSEVERSION from Autocad command line.

Sending from Autocad to Cyclone 3DR

Couldn't find Cyclone 3DR 19.1.4.24386 (19.1.5.24477 found instead) means Cyclone 3DR and Autocad Add-in are not compatible. The Autocad Add-in is installed automatically: each Cyclone 3DR installation replaces the previous add-in. Thus, you have to work with the last Cyclone 3DR version installed on your computer.

Couldn't find a compatible Cyclone 3DR application. Try 3DRCHOOSEVERSION or see the Cyclone 3DR help means:

You forgot to open Cyclone 3DR,
or Autocad tries to connect to the last instance of Cyclone 3DR application launched which was closed. Open again Cyclone 3DR,
or you are not using the same major version on Cyclone 3DR and Autocad Add-in. For instance, you are using Cyclone 3DR 18.1 and you have just installed Cyclone 3DR 19.1; you can switch between major version by typing 3DRCHOOSEVERSION from Autocad command line.

Warning

On some computers, Cyclone 3DR may seem slow after a transfer (usually once a day). Actually, the problem is on Autocad side; you have to close it. Installing again Autocad may be a good answer for the long run.
If you don't see in Autocad the mesh sent from Cyclone 3DR, you can check the command SMOOTHMESHMAXFACE. This command sets the maximum number of faces permitted for mesh objects in Autocad according to your system.