File>Options>Proofing>AutoCorrect Options are a per-installation settings that would not apply when you opening your file on a different computer.
Instead, please try the following steps:
- Create a text box.
- Right-click on the text box border and choose Format Shape. The Format Shape task pane opens.
- Choose Text Options and click on the Textbox icon.
- Select either the Do not Autofit or the Resize shape to fit text options.
- Right-click again on the border of the text box, but this time choose Set as Default Text Box.
- Save the file and upload to OneDrive or SharePoint for use with PowerPoint for the web.