Count of category occurances (multiple cateogries can fall under each row)
All I did was convert all if statements with exact values into a dictionary. This way will allow you to increment the values of each key without as much if/else usage. If you then want to later on pass the values of each key to a variable of your choice, you can just loop through the dictionary once, which is less time consuming and it also makes debugging easier.

I didn't touch the if statements using in. You can try placing it in the dict too.

all_dict = {'customer service':0,
    'long-wait_times':0,
    'contact_issues':0,
    'canada_related':0,
    'product + info':0,
    'design issues':0,
    'gift_wrapping':0,
    'stores':0,
    'email' :0,
    'suggestions':0,
    'rewards':0,
    'registry' :0,
    'returns_cancellations':0
    'technical_issues':0,
    'product_not_available':0,
    'site_performance':0,
    'unable_to_checkout':0,
    'unable_to_add_or_remove_products':0,
    'promotions':0,
    'payment_options':0,
    'paypal':0,
    'shipping_cost':0,
    'order_total_wrong':0,
    'backorder':0,
    'address_not_fitting_or_incorrect':0,
    'where_is_my_order':0,
    'BOPIS':0,
    'delivery_issues':0,
   'no_communication_or_delays':0,
   'damaged_product':0,
  'unassembled_assembly_issues':0
  }

for index, row in df.iterrows():
    for key in (row['taxonomy'] ) :

        if key in technical_issues_list:
            technical_issues += 1

        elif key in checkout_list:
            checkout += 1

        elif key in fulfillment_list:
            fulfillment += 1

        elif  'returns_cancellations' in key:
            returns_cancellations +=1

        else:
            all_dict[key] += 1