Thanks for the screenshot. I ti s now clear to see the issue.
Usually, the WYSIWYG toolbar does not look like this. I think your theme is customizing the toolbar by overriding the button choices.
The kitchen sink is the button on the top row, second from the right and it toggles the second row of buttons. This is not the issue as I can see all the rows are open.
I think you will need to search through your theme for a filter such as ‘tiny_mce_before_init’ and see if there is some code which is changing the buttons.
If this is a purchased theme, perhaps you can also contact the developer and ask them how to allow ACF to add the ‘html’ code button to the WYSIWYG toolbar?
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