The most likely reason is that you run your vbs script as administrator. In such case it is only accessible by administrator.
--allow-other flag is not supported on Windows.
My suggestion is to run it as your normal user. Also simplify it a bit:
dim objShell
Set objShell=wscript.createObject("WScript.Shell")
iReturnCode=objShell.Run(".\rclone.exe mount webdav: O: --vfs-cache-mode write",0,TRUE)
instead of this .\rclone.exe provide full path to rclone
D:\1\rclone-v1.66.0-windows-amd64\rclone-v1.66.0-windows-amd64>rclone lsd webdav: -vv
2024/03/21 10:06:18 DEBUG : rclone: Version "v1.66.0" starting with parameters ["rclone" "lsd" "webdav:" "-vv"]
2024/03/21 10:06:18 DEBUG : Creating backend with remote "webdav:"
2024/03/21 10:06:18 DEBUG : Using config file from "D:\1\rclone-v1.66.0-windows-amd64\rclone-v1.66.0-windows-amd64\rclone.conf"
2024/03/21 10:06:18 DEBUG : found headers:
2024/03/21 10:06:18 ERROR : : error listing: couldn't list files: Propfind "https://xxxx-com:1555/": tls: failed to verify certificate: x509: certificate has expired or is not yet valid:
2024/03/21 10:06:18 DEBUG : 2 go routines active
2024/03/21 10:06:18 Failed to lsd with 2 errors: last error was: couldn't list files: Propfind "https://xxxx-com:1555/": tls: failed to verify certificate: x509: certificate has expired or is not yet valid:
I use cmd to run
.\rclone.exe mount webdav: o: --cache-dir D:\Temp --allow-other --vfs-cache-mode writes --allow-non-empty
D:\1\rclone-v1.66.0-windows-amd64\rclone-v1.66.0-windows-amd64>.\rclone.exe mount webdav: o: --cache-dir D:\Temp --allow-other --vfs-cache-mode writes --allow-non-empty
2024/03/21 10:09:30 NOTICE: --allow-non-empty flag does nothing on Windows
2024/03/21 10:09:30 NOTICE: --allow-other flag does nothing on Windows
2024/03/21 10:09:30 ERROR : webdav root '': Statfs failed: Propfind "https://xxxx-com:1555/": tls: failed to verify certificate: x509: certificate has expired or is not yet valid:
The service rclone has been started.