Can't add later in Artflow

(Updated with solution)

Hi,

I am new to the app and hit the pay wall while working on a project. I needed to add a third layer and watching the advert did not allow me to do so. As I was impressed with the app, I bought it thinking I would get full functionality, however, I still cannot add any more layers. The plus sign is greyed out.

If I start a new project, it allows me to add many layers so it seems there is a bug which stops the upgrade to the paid app being applied to existing projects. 

I have tried restarting the device and reinstalling the app. 

Also, there was another bug which meant the purchase and watch advert options remained in the menu. Reinstalling the app fixed that though. 

I am using a Kindle Fire 8 HD.

I hope someone has an idea how to get around this. 

Thanks for reading.

SOLUTION

After some experimentation, I came to realise there is an upper limit to the number of layers available based on the resolution and size of the canvas. The higher the size and of value, the fewer layers allowed. At max PX and size, only two layers are allowed. Once I reduced both in a new image I could use many more layers. 

I tried increasing the cache size in settings but it did not help.

This is unfortunate, as it means the app is not suitable for high res artwork.

Maybe, the developer could address this issue in the next update.

Other than that, it is a great app!