About the problem, one idea would be to install ImageMagick using the official installer, and then make the changes in the alfresco-global.properties in order to have Alfresco using this manually installed instance instead of the one Alfresco installs.
Other than that, you should be searching for the error in the log:
[localhost-startStop-1] ImageMagickContentTransformerWorker not available: 09090036 Failed to perform ImageMagick transformation: Execution result: os: Windows 10 command: C:\alfresco-community\imagemagick\convert.exe C:\ALFRES~1\tomcat\temp\Alfresco\ImageMagickContentTransformerWorker_init_source_2535584417039233690.gif -strip -quiet C:\ALFRES~1\tomcat\temp\Alfresco\ImageMagickContentTransformerWorker_init_target_8877265038482905492.png succeeded: false exit code: 1 out: err: convert.exe: RegistryKeyLookupFailed `CoderModulesPath' @ error/module.c/GetMagickModulePath/670. convert.exe: no decode delegate for this image format `GIF' @ error/constitute.c/ReadImage/509. convert.exe: no images defined `C:\ALFRES~1\tomcat\tem