Unable to install Chrome or Safari extensions after creating new user account Mac OS X El Capitan 

This ordeal began when I was unable to connect Time Machine to a newly purchased Time Capsule; it still wanted to hang on to an older external drive which had died. I called Apple and they instructed me to create a new user account and try connecting the Time Capsule. This worked and I was able to back up to Time Capsule.

But. Reinstallation of Google Chrome extensions fails. First I see a dialog box I didn't see before:



Then when I click 'Save', it displays this:



And in the download bar, the item is tagged "Failed -- insufficient permissions".

Extension installation fails for Safari also. 

I tried booting into the recovery partition and repairing the user permissions, but that did not solve the problem.

Any ideas?
You don't describe how the Safari extensions fail to install, but if you had the same problem as I you would first get a dialog box saying that something went wrong, and the extension install button is then replaced with a red "installation failed" message. 

I solved this by going into the keychain manager preferences and resetting the default keychain. After that all extensions installed normally.

For some reason, every time I started Safari it asked for the password to the default keychain, and being a freshly installed OS I just typed the only password I had -- my user password -- which it didn't accept. Apparently Safari just couldn't verify the extensions' signatures.

I got the idea while reading Repeated &quot;Safari wants to use the &#39;Local Items&#39; keychain&quot; alert