Most cases not responding to amoxyclav are because of low dose of augmentin ( recommended dose is 2000mg every day for 60 kg adult patient).
Other possibilty is it can be viral infection of tthe throat not bacterial infection, viral infection usually improves within 7 days.
Next Steps
Continue taking Amoxy clav in proper dose and complete at least 7 days,
Health Tips
Amoxyclav is the first line treatment and usually doesn't have resistance.