Add troubleshooting section and initial doc

Author: mlonsk

content/te3/toc.md

@@ -71,6 +71,9 @@
 ### @creating-macros
 ### @csharp-script-library
 
+# Troubleshooting
+## @locale-not-supported
+
 # Other resources
 ## @downloads
 ## @roadmap

content/te3/troubleshooting/locale-not-supported.md

@@ -0,0 +1,51 @@
+---
+uid: locale-not-supported
+title: Locale Not Supported
+author: Morten Lønskov
+updated: 2025-09-02
+applies_to:
+  editions:
+    - edition: Desktop
+    - edition: Business
+    - edition: Enterprise
+---
+# "Locale is not supported" Warning
+
+You may encounter the warning message:
+
+```
+The XXXX locale is not supported
+```
+in the Tabular Editor 3 Message view
+
+This issue usually occurs when your local machine uses a **regional configuration not supported by the Analysis Services (SSAS) engine**.  
+In most cases, the error is triggered by another underlying issue or warning, but this message is shown as a result.
+
+---
+
+## Scenarios and Solutions
+
+### 1. Connecting to a Local SSAS Instance
+If you are running SQL Server Analysis Services (SSAS) locally on your machine:
+- **Solution:** Change the **service account** used by the SSAS instance.  
+  Updating the account often resolves unsupported locale mismatches.
+
+---
+
+### 2. Connecting to a Remote SSAS, Azure AS, or Power BI
+When connecting to a remote instance, you have two possible solutions:
+
+#### Option A: Specify Locale in the Connection String
+Explicitly set a supported locale (e.g., English – 1033) by adding `LocaleIdentifier=1033` to your connection string.
+
+**Example (Azure AS):**
+```plaintext
+Data Source=asazure://westeurope.asazure.windows.net/instance-name;LocaleIdentifier=1033
+```
+
+#### Option B: Change Regional Settings on Your Machine
+Adjust your local system’s regional and language settings to match a supported locale.
+
+- **Recommended settings:**  
+  - **Regional format:** English (United States)  
+  - **Windows Display Language:** English (United States)