Funding plugin - "Fatal error: Call to undefined action. . ." after updating to v. 2.6.1.

Hello,

I just updated the Funding plugin to version 2.6.1.7. The whole site immediately broke with

Fatal error: Call to undefined function is_subdomain_install() in /home/username/subdomain.domain.com/wp-content/plugins/fundraising/fundraiser.php on line 81

Renamed the plugin folder via ftp, downloaded the folder for safekeeping, went back to the wp site and deleted and reinstalled the Funding plugin. Site didn't break this time, but still getting same error when trying to activate the updated plugin.

Site was working just fine before update. Except for the WPMU Dev and Funding, there's only one other plugin installed on this site.

Thanks for your help.