Power Automate allows you to use expressions in actions, conditions, and dynamic content to manipulate data. However, if an expression contains unsupported functions, incorrect syntax, or invalid references, the flow may fail with the following error:
“Unsupported Expression – Using an unsupported function or expression.”
This error typically occurs when:
- Using a function that Power Automate does not support.
- Incorrectly formatting an expression.
- Referencing a function from another programming language (e.g., Excel, JavaScript, or SQL).
- Using a deprecated or unavailable feature.
2. Common Causes of Unsupported Expression Errors
| Cause | Description | Example |
|---|---|---|
| Using a Non-Supported Function | Function is not available in Power Automate. | LEFT('Hello', 2) (Excel function, not Power Automate) |
| Incorrect Syntax | Expression format is invalid. | concat(Hello, World) (missing quotes) |
| Using Programming Syntax from Other Languages | JavaScript, SQL, or Excel syntax used incorrectly. | IF(A1>10, "Yes", "No") (Excel formula, not Power Automate) |
| Using a Function in the Wrong Context | Some functions only work in specific actions. | items('Apply_to_each') outside of a loop |
| Referencing Deprecated or Unavailable Features | Some functions may have changed or been removed. | json('{"name":"John"}') (deprecated) |
3. Step-by-Step Troubleshooting Guide
Step 1: Identify the Unsupported Expression
- Go to Power Automate (https://flow.microsoft.com).
- Open My Flows and select the flow with the error.
- Click Run History and find the failed run.
- Expand the failed action and look at the expression field.
- Note any error message related to an unsupported function or syntax issue.
Example Error Message:
"InvalidTemplate. The function 'LEFT' is not supported in this workflow."
This suggests the function LEFT() (from Excel) is not supported in Power Automate.
Step 2: Check If the Function Is Supported in Power Automate
Power Automate does not support all functions from Excel, SQL, JavaScript, or Power Apps.
Solution: Use Power Automate’s equivalent functions.
Excel Function Alternative in Power Automate:
| Excel Function | Power Automate Equivalent |
|---|---|
LEFT(text, n) | substring(text, 0, n) |
RIGHT(text, n) | substring(text, length(text) - n, n) |
MID(text, start, length) | substring(text, start, length) |
IF(condition, true_value, false_value) | if(condition, 'true_value', 'false_value') |
Example Fix:
Incorrect:
LEFT('Hello', 2)
Correct:
substring('Hello', 0, 2)
Step 3: Ensure Correct Syntax for Expressions
Expressions must be correctly formatted with proper quotes, commas, and function structures.
Solution: Ensure the correct syntax for Power Automate functions.
Common Functions & Correct Syntax:
| Function | Correct Usage | Incorrect Usage |
|---|---|---|
| concat() | concat('Hello', ' World') | concat(Hello, World) (missing quotes) |
| length() | length('Power Automate') | length(Power Automate) (missing quotes) |
| if() | if(equals(2, 2), 'Yes', 'No') | IF(2=2, "Yes", "No") (Excel-style) |
Example Fix:
Incorrect:
concat(Hello, World)
Correct:
concat('Hello', ' World')
Step 4: Use Functions in the Correct Context
Some functions only work inside specific actions.
Solution: Make sure the function is being used in the correct scope.
Example Fix:
Incorrect (using items() outside of a loop):
items('Get_items')?['Title']
Correct (use within Apply to Each loop):
items('Apply_to_each')?['Title']
Step 5: Replace Deprecated or Unavailable Functions
Some older functions may no longer work in new versions of Power Automate.
Solution: Use alternative supported functions.
Example Fix:
Incorrect:
json('{"name":"John"}')
Correct (Use parseJSON() in “Parse JSON” action):
parseJSON('{"name":"John"}')
Step 6: Test the Updated Expression
- Modify the expression using a supported function.
- Click Save and then Test the flow manually.
- Check if the error disappears.