Reference the IDs in addition to the classes, for example:
$(parentForm + " .productsubmit").removeAttr("disabled").removeClass("foxyshop_disabled");
to
$(parentForm + " .productsubmit, " + parentForm + " #productsubmit").removeAttr("disabled").removeClass("foxyshop_disabled");
We can help FoxyShop users who have custom templates by making the previous changes for some IDs to classes backward-compatible. Specifically, this change: https://github.com/FoxyCart/foxyshop/pull/45/files#diff-ddb5a5c7456b15c787c4a0d1a93d384d899fafd5d6d994341b418ec2edfa7f0fL190-R191
Reference the IDs in addition to the classes, for example:
$(parentForm + " .productsubmit").removeAttr("disabled").removeClass("foxyshop_disabled");
to$(parentForm + " .productsubmit, " + parentForm + " #productsubmit").removeAttr("disabled").removeClass("foxyshop_disabled");