Activation Error

Getting the following error after activating the plugin:

fopen(CMTT_PLUGIN_FILE): failed to open stream: No such file or directory in /home/xxx/public_html/wp-includes/functions.php 4785

fread() expects parameter 1 to be resource, boolean given in /home/xxx/public_html/wp-includes/functions.php 4788

fclose() expects parameter 1 to be resource, boolean given in /home/xxx/public_html/wp-includes/functions.php on line 4791

Running PHP 7.0.19
allow_url_fopen is on
mod_rewrite is working
mbstring is enabled
cURL is enabled

Tried installing with no other plugins and using the TwentyFifteen theme, get the same errors.
Tried deleting and re-installing by uploading (instead of auto install), same errors.

When I try and look at CM Answers->Settings from Dashboard I get this additional error:
Fatal error: Uncaught Error: Call to a member function getOption() on null in /home/xxxxx/public_html/wp-content/plugins/cm-answers/package/cminds-free.php:1828 Stack trace: #0 /home/xxxxx/public_html/wp-includes/shortcodes.php(345): com\cminds\package\free\v1_0_8\CmindsFreePackage->showRegistration(Array, ”, ‘cminds_free_reg…’) #1 [internal function]: do_shortcode_tag(Array) #2 /home/xxxxx/public_html/wp-includes/shortcodes.php(223): preg_replace_callback(‘/\\[(\\[?)(cminds…’, ‘do_shortcode_ta…’, ‘[cminds_free_re…’) #3 /home/xxxxx/public_html/wp-content/plugins/cm-answers/views/backend/settings.phtml(1): do_shortcode(‘[cminds_free_re…’) #4 /home/xxxxx/public_html/wp-content/plugins/cm-answers/lib/controllers/BaseController.php(598): require(‘/home/xxxxx/…’) #5 /home/xxxxx/public_html/wp-includes/class-wp-hook.php(298): CMA_BaseController::displaySettingsPage(”) #6 /home/xxxxx/public_html/wp-includes/class-wp-hook.php(323): WP_Hook->apply_filters(”, Array) #7 /home/xxxxx/public_ht in /home/xxxxx/public_html/wp-content/plugins/cm-answers/package/cminds-free.php on line 1828