What Add-in are you using?
This issue is not relevant to the Office 365 Add-in, as the result display will follow the design template setup.
When you launch a word cloud poll and the result image appears off-centered, you need to change the PowerPoint slide size you are currently using.
In order for Vevox to work effectively, your slides sizes must be set to:
- Widescreen 16:9 and
- The default widescreen dimensions.
These dimensions are: 33.867cm by 19.05cm - or- 13.333in by 7.5in.
Once you change your slide size to the above dimensions, you will see the word cloud appears centered again.