Fatal Error: Stripe\Stripe not found error

Hi,

I keep getting this error, whether it uses our theme or the twenty sixteen theme:

[Wed Aug 30 18:09:07.530267 2017] [:error] [pid 20477] [client 127.0.0.1:64296] PHP Fatal error:  Class 'Stripe\\Stripe' not found in .../wp-content/plugins/wp-simple-pay-pro-3/includes/payments/stripe-api.php on line 42, referer: https://possible.ynah/test-stripe/

I have all plugins disabled but this one and it’s still rendering the same error. Here’s a copy of my system status report:

### WordPress Installation ###

Site Name: Possible
Home URL: http://possible.ynah
Site URL: https://possible.ynah
SSL/HTTPS Enabled: Yes
Version: 4.8.1
Locale: en_US
Multisite: No
Permalinks: /%category%/%postname%/
WP Memory Limit: 40 MB
WP Debug Mode: No
Script Debug: No

### WP Simple Pay Pro Settings ###

WP Simple Pay Pro Version: 3.1.2
Stripe TLS: TLS 1.2 is supported. No action required.
Simple Pay Test or Live Mode: Test Mode

### Active Theme ###

Theme: Twenty Sixteen - 1.3
Child Theme: No
Parent Theme: -

### Active Plugins ###

WP Simple Pay Pro 3: 3.1.2

### Server Environment ###

Web Server: Apache/2.4.25 (Unix) LibreSSL/2.2.7 PHP/5.6.30
PHP Version: 5.6.30
MySQL Version: 5.6.21
Server Timezone: UTC
Display Errors: No
Server PHP Memory Limit: 1024M
Upload Max Filesize: 40M
Post Max Size: 40M
Max Execution Time: 30
Max Input Vars: 1000
fsockopen: Yes
cURL: 7.54.0
SecureTransport
SOAP: Yes
SUHOSIN: No
WP Remote POST: Yes
WP Remote GET: No (cURL error 28: Resolving timed out after 5096 milliseconds)

### Client Information ###

IP Address: 127.0.0.1
Browser: Chrome 60.0.3112.101 (Apple)

This all happening on my local so I can’t give you a test link.

Thanks.