This is an ongoing issue but I cannot find the original bug report anymore.
Affects versions (on my switch tested) from 1.20.41 till now 1.21.72 (just updated and tested).
When Í click a previously stored game or (re)start a game:
it opens a download box to download the Natural-texture pack instead, however the texture pack is already downloaded.
Then a popup tells me the texture pack could not be downloaded and I should restart the game or re-download the texture pack.
Neither given suggestions work and I return to point 1
Work around:
remove any texture pack in the resources of the chosen game to load (edit game settings of the world you wanted to load).
Go back to the start screen before the screen to choose a game to load (home screen)
Choose settings and navigate down to general resources and click it.
Remove any texture pack here activated in the General resources settings.
Return to the start screen (click B ) , wait for the popup telling you it is “loading (general) resources, this might take a while”
Now the standard texture (and color) home screen should be loaded with the grey buttons for play, settings and market place. Choose settings again.
Navigate to general resources again and add the desired texture pack, in my case the Minecraft Natural-texture pack, click activate
Click button B again to return to the home screen, a popup is telling you it is loading resources again, you will see the screen change according to the texture map chosen again (with a few glitches).
Without hitting any other button, now directly go to play and when the available worlds appear, directly choose the world you want to play and click A
Now the game will load directly,….. with your chosen texture pack,
or you will be prompted again with an attempt to download the texture pack and give the same error, if this is the case, go back to point 2 and try again.
I sincerely hope this will be fixed soon because it is really annoying…
This issue is being tracked at MCPE-180918.