port on UNO compatible boards

I have 2 UNO compatible boards that both run on my windows 10 desktop but use different ports. I'm also using my chrome laptop and one of the boards works fine but the other not when using the online development system. There seems to be no way to change the port used

Windows assigns the port, not the Uno. You can change the port via Windows Device Manager but I wouldn't mess with it. As for Chrome, I have no clue because I've never used it.

Chrome OS might not have the relevant driver for the board that is not working.

If you just plug in the one board that is not working, does Create display a board is connected?

Where is Create? I'm using Arduino Editor on a chromebook. In the box where the board type is displayed there is a red X at the left hand side which presumably means that it hasn't recognised the board.
When I used the downloaded programming tool on my desktop both boards work but I need to change the port number between the 2 boards.

In the box where the board type is displayed there is a red X at the left hand side which presumably means that it hasn't recognised the board.

Can you click this area to select a new board?

I can click on it and get the screen with the list of boards. None are ticked. If I tick on Arduino/Genuino then there is only one option for the port. returning there is still a red cross at the left hand side of the box showing the board type.

Would you be able to take a screenshot of photo of the dialog with:

  1. No boards connected
  2. Only the first board connected
  3. Only the second board connected
  4. Both boards connected

Here are the 4 screenshots.
When using these boards with the downoaded Arduino program on my windows10 desktop they both work but the one I have a problem with on Create only works if port 4 is selected and the ok one is port 1.

We need the dialog after clicking the "Arduino/Genuino Uno" area.

It still appears that Chrome OS doesn't have a driver for one of the boards.

As the problem board does not work on port 1 on my windows 10 desktop but only when port 4 is selected, it looks to me as though this board uses port 1 for something else. If so, maybe Create requires to use port 1 and that is why it doesn't work?

OK. Now I have tried running Create on my win10 desktop and it works fine with both boards. The one I had the problem with running create on my chromebook installed on on the desktop but was set to port 4 as it was on the IDE, There seems to be no facility for setting ports on the chromebook installation of Create so I guess this is a bug (or feature!) of the system.
It would be very helpful if there was a way around this.