[ERROR] DotNet required, but it's not installed

Hi, i have installed the lastest beta version and the .NET 5 on my raspberry.
When i run manually the ./run.net.sh, all it's ok. Webgrab works fine.
But when i crontab directly the script, i have an error message : DotNet required, but it's not installed

My raspberry log :

root@raspberrypi:~# dotnet

Usage: dotnet [options]
Usage: dotnet [path-to-application]

Options:
-h|--help Display help.
--info Display .NET information.
--list-sdks Display the installed SDKs.
--list-runtimes Display the installed runtimes.

path-to-application:
The path to an application .dll file to execute.

root@raspberrypi:~# dotnet --info
SDK .NET (reflétant tous les fichiers global.json) :
Version: 5.0.406
Commit: 3a48fd6fe5

Environnement d'exécution :
OS Name: raspbian
OS Version: 10
OS Platform: Linux
RID: linux-arm
Base Path: /opt/dotnet/sdk/5.0.406/

Host (useful for support):
Version: 5.0.15
Commit: 3065735be7

.NET SDKs installed:
5.0.406 [/opt/dotnet/sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 5.0.15 [/opt/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 5.0.15 [/opt/dotnet/shared/Microsoft.NETCore.App]

To install additional .NET runtimes or SDKs:
https://aka.ms/dotnet-download

Have you an idea of the issue ?? thanks