
Hi @Tevon2.0 ,
Thanks for the post.
According to the research and test, you could enable custom script by using PowerShell command.
- Login to your SharePoint Farm SharePoint 2019 On-Premise
- Open SharePoint 2019 Management Shell as administrator
- Execute the following PowerShell command: (Get-SPSite -Identity "https://your-host/sites/modern-site").DenyPermissionsMask = [Microsoft.SharePoint.SPBasePermissions]::EmptyMask
For more information: Activate Custom Script for SharePoint 2019
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I hope I can offer you a better experience next time if I have a chance to work with you again.
Yours faithfully,
Renjie Sun
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