If you’re having trouble logging in to the **OpenProject Mobile App**, the following sections will help you identify and resolve the most common issues.

## 1\. Invalid or Inaccessible Instance URL

**Symptom:**  
You see an error such as _“We can't connect with the instance URL. Please, check possible solutions here”_

**Cause:**  
The URL you entered may be incorrect, inaccessible, or not using HTTPS.

**How to Fix:**

*   Double-check the URL format (e.g., `https://yourcompany.openproject.com`).
    
*   Ensure your instance is publicly accessible and uses **HTTPS** (HTTP is not supported).
    
*   Try opening the same URL in your mobile browser to confirm connectivity.
    

## 2\. OAuth Application Not Enabled

**Symptom:**  
Login fails with an error such as _“We can't complete the OAuth Authentication. Please, check possible solutions here”,_ or you are redirected back to the login screen without authentication.

**Cause:**  
The mobile app uses OAuth 2.0 for secure authentication. If the built-in OAuth applications are not enabled in your instance, the app cannot log you in.

**How to Fix:**

1.  Go to your OpenProject administration area at:  
    `{BASE_URL}/admin/oauth/applications`
    
2.  Make sure that **Built-in OAuth applications** are enabled.
    
3.  If you don’t have admin rights, contact your OpenProject administrator.
    

## 3\. Instance Not on Minimum Supported Version

**Symptom:**  
You receive an error such as _“Instance not on minimum supported version: OpenProject 17.0.0”_, or the authentication window fails to open.

**Cause:**  
The OpenProject Mobile App requires your instance to be on **OpenProject version 17.0.0 or later**.  
If your instance is running an older version, OAuth authentication may be disabled by default.

**How to Fix:**

*   Ask your OpenProject administrator to check the current version of your instance.
    
*   Update to newer version of OpenProject.
    
    *   If updating is not am option, the administrator can **temporarily enable OAuth authentication** by removing the feature flag under:  
        `{BASE_URL}/admin/settings/experimental`
        
    *   Once this flag is removed, the built-in OAuth applications will be available in `{BASE_URL}/admin/oauth/applications`, once enabled the users can log in via the mobile app.
        

_💡 **Note:** Upgrading to the latest OpenProject version is recommended for the best compatibility and security._

## 4\. Invalid SSL Certificate

**Symptom:**  
You receive a message such as _“Secure connection failed. Untrusted certificate”._

**Cause:**  
Your OpenProject instance must use a **valid, signed SSL certificate** (HTTPS). Self-signed certificates or expired certificates are not supported.

**How to Fix:**

*   Verify that your SSL certificate is valid and trusted by your device.
    
*   If you’re using a self-signed certificate, replace it with one from a trusted certificate authority (CA).
    

## 5\. Wrong Credentials

**Symptom:**  
You see _“Invalid username or password”_ when logging in.

**Cause:**  
Your login credentials are incorrect or have been changed.

**How to Fix:**

*   Make sure you’re using your **OpenProject account credentials**, not your email alias (unless configured as your username).
    
*   Try logging in via the web version of OpenProject to confirm your credentials.
    
*   Reset your password if necessary.
    

## 6\. On-Premises API Access Disabled

**Symptom:**  
Login attempts fail with no clear error message.

**Cause:**  
Your on-premises OpenProject instance may have **API access disabled**, preventing the mobile app from connecting.

**How to Fix:**

*   Log in as an administrator and navigate to:  
    `Administration → System settings → API`
    
*   Ensure that **API access** is enabled.
    
*   Save changes and try logging in again.
    

## 7\. Instance Using HTTP Instead of HTTPS

**Symptom:**  
The app refuses to connect or shows _“Secure connection failed. Untrusted certificate”._

**Cause:**  
The mobile app only supports secure connections via **HTTPS**.

**How to Fix:**

*   Configure your instance to use HTTPS with a valid certificate.
    
*   Redirect HTTP traffic to HTTPS using your web server configuration.
    

## 8\. Firewall or Network Restrictions

**Symptom:**  
Login attempts time out or fail when using certain networks with an error such as “Login time out. Check your network”.

**Cause:**  
Corporate or restricted networks may block outbound requests to your OpenProject instance or authentication endpoints.

**How to Fix:**

*   Check the network connection of your device. Internet access is required for the app to work.
    
*   Try connecting from a different network (e.g., mobile data).
    
*   Ask your IT team to whitelist your OpenProject domain.