TYPO3与YAG扩展无主题选择FE错误

i have a simple web server at strato.de on which TYPO3 (v7.6.9) is installed. Next I tried to use the YAG (v4.1.2) (Yet Another Gallery) Extension. What I've done:

  1. install YAG from TER (includes pt_extbase, pt_extlist)
  2. create YAG sysfolder
  3. create extension template which includes '[yag] Yet Another Gallery (yag)'
  4. create some albums / galleries and upload images

  5. add new content by plugin:

    • Plugin Mode: Gallery List
    • Choose some sources
    • Theme: Nothing to choose (empty select boy)

Install a new Theme Package, noting changes

If i try it without any theme I got a FE error:

The theme identifier was not set. Please check your TypoScript configuration.

I don't now what I can do. Perhaps someone can help me.

As far as I can see you did everything right. Look again if the template is correct and active on the page you want it to be. Clear all caches. I had a similar problem before and those were the problem.

Change the file \typo3conf\ext\yag\Configuration\TypoScript\Backend\setup.txt to Setup.txt (uppercase S).

Clear the cache, try again.

This is some kind of bug. This trick worked for me in both TYPO3 v7 and v8.