Question: After renaming my heroku app from the heroku website, whenever I cd to its directory in a terminal and run any heroku command, I get `App not found`. Does anybody know of a way to remedy this?

Answer: 
There is another way, you can fix it by renaming the app to the original name via web.

To find out the old name use heroku command line: 

```
> heroku rename newname

```

which will spit out the old name. Use the old name to rename the app via web. You can check if renaming success by running 

```
> heroku info

```

Once done you can rename to the preferred name by using

```
> heroku rename preferredname

```
James Ward's solution didn't work for me. I had to enter my git url in a different format:

```
git remote rm heroku
git remote add heroku https://git.heroku.com/appname.git

```