I am posting this thread in the hope of helping someone in the future.

Dji Action Pro 5 asks you to activate the product after buying it. I can only use the device 5 times if not activated. The only way to activate your DJI device is through the Mimo app. You can get it by scanning the QR code. My first feedback is that this app is not in the official Playstore and is humungous.

Below are the problems I encountered and the solutions that worked for me.

Problem 1: I did not have a successful "phone" to "DJI" device connection the first time.

• What worked for me: Disable my phone's auto-connect to my known network. I also made sure that I was not using mobile data. (Why does the application have to be so intrusive?). I connect to the device's network manually, then restart the application while connected to the device's network.
• My Observation: The Mimo app seems to "attempt" to connect to the device's network so that the phone and the device have their exclusive connection.
• Other things I did that failed: Restart the DJI device, restart the network connection, and clear and forget network connection settings. At this point, I thought I might not activate the device. But I'm glad it did.
  

Problem 2: Updating the firmware.

What worked for me: Disable my phone's auto-connect to my known network. I also made sure that I was not using mobile data. (Why does the application have to be so intrusive?). I connect to the device's network manually, then restart the application while connected to the device's network.

Yes, I know it's Copy and paste. But the bottom line is that you gotta "help" both the DJI device and Android phone to connect.

Further details on how I updated the firmware of my DJI device:

• I turned off the DJI device to prevent it from interfering with the firmware download.
• On my Android phone, I cleared the Mimo's cache. You can find the clear-cache menu somewhere in the profile icon.
• I closed the Mimo app.
• I connected my Android Phone to the internet through my wifi.
• I opened the Mimo app and let it download the firmware. You can let Mimo download the firmware by setting it to auto-download the firmware when connected to wifi that has internet. Another way is that you can explicitly download the firmware yourself. You can tell the download is complete if the cache is no longer growing.
• The last steps are: "Properly" connect the device and your phone to have an exclusive network connection. Tap on the "icon" that says something about installing the firmware to start the firmware update.
  

Some things to note here:

The update requires a complete download of the firmware FROM THE INTERNET, so make sure your phone has internet via your wifi so that Mimo can download the firmware update. On the other hand, the Mimo app can NOT download the firmware when the phone is connected to the DJI device because there is no internet connection.

Here's how I connected my Android phone to DJI

• Disable Android's auto-connect to the known network. You should be able to do this in the settings of each known network on your phone.
• Ensure that DJI's battery is above 50% (other forums say 30% is enough). Plugging the device into a power source ensures the device has power.
• Turn on DJI and give it time to start its network. I reckon about a minute or two should suffice.
• Start Mimo and attempt to connect to the device. At this point, I observed on my Android phone that the device's network is now visible  (you can swipe down your Android screen to navigate to show the available network).
• I manually connect to the device's network by entering the correct password. You can locate the password in the device's wireless connection setting.  Remember that your Android phone stores the password of each known network, so you won't have to enter the password every time.
• The Mimo app could be complaining about being unable to connect during this time (at least in my case). Just ensure that your Android phone is NOW in the DJI's network.
• "Quickly" restart the Mimo app and touch the "camera" icon to let it connect to your device. I notice that the network is gone after about a minute. So, you have to restart the Mimo app before the network connection is severed.
  

Don't worry if you don't get the steps right the first time. It took me a few tries to get this right.

I am hopeful this helps and that the DJI team will resolve all issues with their app.

Hi there, thanks for your valuable suggestions. It is because of more and more dedicated users like you that our DJI products and services can become better and better. Please rest assured that we will register the information and provide feedback to the related departments for evaluation. In the future, we will optimize and improve the product or service based on user comments. Thank you for your support and understanding.