If you have recently started experiencing SharePoint connectivity issues in D365FO such as failed template downloads or 403 Forbidden errors this may be related to the ongoing deprecation of the IDCRL (Legacy SharePoint Authentication) protocol by Microsoft, which we have already described in this forum post: How Deprecation of IDCRL Authentication Affects Docentric SharePoint Integration - Docentric Forum
You can find more details about this on the Microsoft Community Hub: Legacy SharePoint Authentication (IDCRL) Is Retiring - What to Do Before May 1, 2026
Why is this happening?
Microsoft is rolling out the IDCRL deprecation across tenants in stages, which means some customers may be affected earlier than others. If your tenant has already had IDCRL disabled, SharePoint-related functionality in Docentric such as downloading report templates stored in SharePoint will stop working.
Permanent Solution 
Upgrade Docentric to version 3.5.1.2 or newer, which fully supports the new modern OAuth authentication and resolves this issue permanently. We strongly recommend upgrading as soon as possible.
Temporary Workaround 
(Valid until April 30, 2026)
If you are experiencing a critical issue in your production environment and need an immediate fix while planning the upgrade, you can temporarily re-enable IDCRL using the following PowerShell scripts.
First, connect to your SharePoint tenant and retrieve the current settings:
powershell
Install-Module -Name Microsoft.Online.SharePoint.PowerShell
Connect-SPOService -url "https://YOUR_TENANT-admin.sharepoint.com"
$TenantSettings = Get-SPOTenant
$TenantSettings.AllowLegacyAuthProtocolsEnabledSetting
$TenantSettings.LegacyAuthProtocolsEnabled
Please save the existing values as a backup before proceeding.
Then, set both flags to true (Global Admin or equivalent permissions required):
powershell
Set-SPOTenant -AllowLegacyAuthProtocolsEnabledSetting $true
Set-SPOTenant -LegacyAuthProtocolsEnabled $true
Note: This workaround is only valid until April 30, 2026, after which Microsoft will permanently disable IDCRL. Please make sure to upgrade to Docentric 3.5.1.2 before that date.