Guzzle Object could not be converted to string

[duncan-qabana]

I have used this library for some months now. Since 2 days, I am getting errors when connecting to Exact.
The first is:
Fatal error: Uncaught exception 'Exception' with message 'Could not connect to Exact: Client error: 'POST https://start.exactonline.nl/api/oauth2/token' resulted in a '400 Bad Request' response: 'Bad Request' in /vagrant/valvomo/include/application/class.Exact.php:901 Stack trace: #0 /vagrant/valvomo/include/application/class.Exact.php(40): Exact->connect(Array) #1 /vagrant/mijn/index.php(1040): Exact->index('10', Array) #2 {main} thrown in /vagrant/valvomo/include/application/class.Exact.php on line 901

After some debugging, I found:
Catchable fatal error: Object of class GuzzleHttp\Client could not be converted to string in /vagrant/vendor/picqer/exact-php-client/src/Picqer/Financials/Exact/Connection.php on line 114

But I have no clue how to fix it, going deeper is going into the src code of Guzzlehttp. Do you have a fix?

[duncan-qabana]

Never mind, somehow the old keys were cached and weren't pulled from the storage. Chaos ensued.