"To contact the manufacturer" means to get in touch with the company or person who made a product or item in order to ask questions, report issues, or make inquiries about the product. Full definition
When in doubt, do not buy or use a product before contacting the manufacturer for verification that the product is free of gluten. (thespruce.com)
Please contact the manufacturer directly for technical support and customer service. (apple.com)
Please contact the manufacturer of your water treatment system directly to find out where replacement filters are sold for your specific unit. (nsf.org)