Missing action input – An action is missing required input data for processing.

In Power Automate, every action requires specific input data to execute successfully. The error “Missing Action Input” occurs when:

The required input field is empty.
The action is expecting dynamic content that is missing.
A previous step did not return data, causing the action to fail.

This guide explains:
🔹 Common causes of the “Missing Action Input” error
🔹 How to diagnose and fix the issue
🔹 Best practices to prevent missing input errors

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Step 1: Understanding the “Missing Action Input” Error

Power Automate actions require input values to execute correctly. When input is missing, the flow cannot proceed.

Common causes of missing input:

Cause	Description
Dynamic content is missing	The action references dynamic content that wasn’t provided.
Previous action failed	The step that generates the input data did not execute successfully.
Incorrect variable assignment	A variable was not initialized or assigned a value before use.
Condition skipped required action	A previous condition prevented the required action from running.
User input missing	Manually entered data was not provided when triggering the flow.

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Step 2: Diagnosing the Issue

2.1. Check Flow Run History for Errors

1. Open Power Automate (https://make.powerautomate.com).
2. Navigate to My Flows → Select the failing flow.
3. Click Run History and open a failed run.
4. Identify the action with the “Missing Action Input” error.
5. Look at the expected input fields and check if they contain values.

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Step 3: Fixing the “Missing Action Input” Error

3.1. Ensure Dynamic Content is Available

Problem: The action references dynamic content that wasn’t generated.

Solution:

• Open the Dynamic Content panel and verify that the field exists.
• If missing, ensure that the previous step outputs the required data.
• Use the “Coalesce” function to provide a default value.

Example: Handling missing dynamic content gracefully

coalesce(outputs('PreviousAction')?['body/value'], 'Default Value')

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3.2. Fix Previous Action Failures

Problem: The previous action failed, preventing the required input from being generated.

Solution:

• Go to Run History and check if the previous action failed.
• Fix the root cause of the failure (e.g., API error, missing data).
• Configure “Run After” settings to handle failures gracefully.

How to Configure Run After:

1. Click the three dots (...) on the dependent action.
2. Select “Configure run after”.
3. Choose “is successful” or “has failed” to handle errors.

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3.3. Validate Input Variables Before Use

Problem: The flow references a variable that was never initialized or assigned a value.

Solution:

• Use an “Initialize Variable” action at the start of the flow.
• Before using a variable, ensure it contains a valid value.

🔹 Example: Preventing a failure if a variable is empty

Condition: If variable('InputValue') is empty → Set a default value.

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3.4. Fix Condition Skipping a Required Action

Problem: A condition prevented an action from running, leading to missing input.

Solution:

• Ensure that required actions are always executed before the input-dependent action.
• Modify the condition logic to prevent important actions from being skipped.

🔹 Example: Checking if a value exists before proceeding

Condition: If outputs('PreviousAction')?['body/value'] is empty → Stop the flow or set a default value.

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3.5. Ensure User Input is Provided

Problem: A manually triggered flow expects user input, but none was provided.

Solution:

• Mark input fields as required in manually triggered flows.
• Add default values to prevent missing input errors.
• Validate user input before proceeding with processing.

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Step 4: Preventing Future Missing Input Errors

✅ 4.1. Always Validate Inputs Before Use

• Use conditions to check if input values exist before executing actions.
• Provide default values when possible.

✅ 4.2. Implement Error Handling & Retry Policies

• Configure “Run After” settings to handle missing input gracefully.
• Enable “Retry Policy” on actions that might fail due to missing data.

✅ 4.3. Use Fallback Values for Dynamic Content

• Use “Coalesce” to provide a fallback value when referencing dynamic content.

✅ 4.4. Monitor Flow Performance & Set Alerts

• Regularly check Run History for missing input errors.
• Set up alerts when an action receives unexpected null values.

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Step 5: Setting Up Alerts for Missing Inputs

To detect missing inputs early, set up an alert:

1. Add a “Condition” action before a critical step.
2. If the expected input is missing, send an email alert.
3. Example: If outputs('PreviousAction') is empty → Send alert email "Missing Input Detected!"