Ipad app will not rotate to landscape

You’re in good company.

I heartily dislike Apps that force the iPad in to Portrait mode - as, arguably, iPad is predominantly intended/designed to be used in Landscape mode. Nearly every mainstream Keyboard (e.g., Apple “Magic” and “Smart” keyboard) or folio solution is designed for Landscape - and when you screen is forced by a App into Portrait, the package becomes unusable.

Given the rigorous vetting of Apps against Apple’s App design rules, it seems perverse that sloppy/lazy UI design should be acceptable for iPad.

Some Apps, annoyingly, are not designed by the App Developer to operate in Landscape screen-mode. This is not the fault of the Operating System, but is instead either “by design” or omission by the respective Developer.

This malady is most often observed in Apps principally designed for an iPhone.

Where an App is coded to work In both Portrait and Landscape modes, the Operating System can be configured to force display in the preferred screen orientation.

The Apps themselves need to support rotation. You can't force the App to rotate if it is not designed to do so.

You'll need to find one that supports Landscape mode.

A quick search in the App store was able to find this one, which, going by the screen shots, is in Landscape mode: ‎Slideshow Master - MV maker on the App Store