With runny nose and cough, this is most likely a viral upper respiratory infection, and 12 hours is far too early to call Dolo a failure. Paracetamol only brings fever down for 4-6 hours; it does not cure the infection, and viral fever normally settles over 3-5 days. Keep Dolo 650 strictly 6-hourly SOS above 100F, not randomly.
Next Steps
Steam inhalation twice a day, warm salt-water gargles, 3 litres fluids, and plain rest for the next 48 hours. If fever is still crossing 100F on day 4, get CBC, dengue NS1 and urine routine done. Book a Practo consult with me if it drags on and I will decide whether antibiotics are actually needed.