Follow below instructions:
Quit Creative Cloud desktop application and close All Adobe applications.
Follow below steps :
Step 1 :
1) Right click on Finder icon and select "Go-To" Folder option.
2) You will get a text box, type-in below command and then hit 'Return' key.( Do not miss ~ symbol)
~/library
3)Then navigate to Application Support>Adobe
.
Right click on Adobe folder and select "GetInfo" option.
Expand the Sharing & Permissions section.
Click the lock icon in the lower-right corner. Enter your administrator user name and password when prompted, and then click OK.
Please click on '+' symbol , it will open list of user accounts. Add Currently logged in user name and Administrator option,
Then provide "Read & Write" permission to Currently logged in user name and Administrator option,.
Click the Gear icon, and select Apply to Enclosed Item. Close the Get Info dialog box.
Step 2:
1) Right click on Finder icon and select "Go-To" Folder option.
2) You will get a text box, type-in below command and then hit 'Return' key.
/library
3)Then navigate to Application Support>Adobe
.
Right click on Adobe folder and select "GetInfo" option.
Expand the Sharing & Permissions section.
Click the lock icon in the lower-right corner. Enter your administrator user name and password when prompted, and then click OK.
Please click on '+' symbol , it will open list of user accounts. Add Currently logged in user name and Administrator option,
Then provide "Read & Write" permission to Currently logged in user name and Administrator option,.
Click the Gear icon, and select Apply to Enclosed Item. Close the Get Info dialog box.
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Then launch Creative Cloud desktop application and try to install Flash App again.