How do I keep PowerPoint from defaulting spellchecker back to Portuguese when Spellchecker is set to English - US?

Reset the presentation’s existing text to English (United States), then set PowerPoint’s DefaultLanguageID to US English so newly created objects do not revert to Portuguese.

PowerPoint stores proofing language on individual text ranges, independently of Office’s display and authoring-language preferences. That is why this can affect PowerPoint alone even though Windows and the other Office applications are correctly configured. ^1^

Correct the current presentation

1. Open the affected presentation.
2. Go to Review → Language → Set Proofing Language.
3. In the dialog shown in your screenshot:
   • Select Document to update the presentation, if that option is available.
   • Choose English (United States).
   • Ensure Do not check spelling is cleared.
   • Select OK.
4. If Document does not update every object, select the text in each affected text box or placeholder and repeat Review → Language → Set Proofing Language → English (United States).

PowerPoint does not provide Word’s Detect Language Automatically feature, so that setting cannot be used to correct this automatically. Languages shown near the top of the language dialog are languages currently in use in the document; therefore, Portuguese appearing there indicates that at least some selected presentation text is tagged Portuguese—it does not mean Portuguese is your Windows or Office authoring default. ^2^

Set US English for future PowerPoint text

The PowerPoint object model exposes a presentation default that can be reset directly. This setting applies to newly created objects; it does not retag existing text. Microsoft also documents that changing it affects new and subsequently opened presentations, not only the active file. ^3^

1. In PowerPoint, press Alt+F11.
2. Select Insert → Module.
3. Paste and run this macro with F5:

Sub SetPowerPointDefaultToEnglishUS()
    ActivePresentation.DefaultLanguageID = _
        msoLanguageIDEnglishUS
    MsgBox "PowerPoint default language is now English (US)."
End Sub

Because this changes the default for subsequently opened presentations, use it only if English (United States) should be your normal PowerPoint proofing language.

Save the current file after separately correcting its existing text. The macro alone will not change Portuguese tags already stored in text boxes, placeholders, tables, grouped objects, SmartArt, notes, masters, or layouts.

If Portuguese returns in only one template

The source template or reused slide content may still contain Portuguese-tagged text. Open the template or original presentation and correct its placeholders and reusable content rather than repeatedly correcting generated presentations.

Check:

1. View → Slide Master.
2. Inspect the master and each layout used by the affected slides.
3. Select editable placeholder text and apply Review → Language → Set Proofing Language → English (United States).
4. Close Master View and save the corrected template.

PowerPoint has reported limitations involving proofing-language settings in master slides, so test the corrected template by creating a new presentation and typing into a new placeholder. ^4^

The French, Spanish, Portuguese, and Arabic sections under File → Options → Proofing are not evidence that the selected text is currently being proofed in those languages. The decisive indicator is the language assigned in Set Proofing Language for the selected text.

If Portuguese still appears in an entirely new blank presentation after running the default-language macro, the behavior is no longer confined to stored tags in an existing file or template. At that point, update or repair Microsoft 365 and open a Microsoft 365 support case with a minimal blank presentation that reproduces the issue.

References

1. TextRange.LanguageID property (PowerPoint)
2. [Windows 11](https://support.microsoft.com/word/set-up-or-change-the-languages-used-to-check-spelling-and-grammar)
3. Presentation.DefaultLanguageID property (PowerPoint)
4. Powerpoint proofing language settings in master slides are ignored - Microsoft Q&A