HVAC not cooling in summer weather both floors and sun room

[Gp G.]

Hi

Tenant is complaining cooling not happening in the property. It is new HVAC system put about 1 year ago. This property has 2 floors upstairs has  there are 3 bedrooms.  Previous tenants used to have pets and about 10 people used to live who made place bit mess.  HVAC contractor mentioned earlier ducts, vents are kind of blocked with pet hair etc. How to clear pet hair from hvac ducts and vents. There is one sun room downstairs which is not cooling properly as lot of windows on the sides and top for that sunroom. Also tenant keeping lot of stuff blocking ducts and vents proper air flow as well. I see tenant keep putting these type requests frequently and costing around couple of hundred dollars to me to send HVAC contractor for his trip fee. HVAC contractor keep saying no issue with new HVAC system all working as expected and all pressure readings are good every time he visits. One time HVAC contractor mentioned better to put air boosters in upstairs. Also one problem is tenant kee travelling lot of days of week by switching off the HVAC system. When she come back from travel when she switch on HVAC it takes long time for her to cool entire 2000 square feet property. Any tips or suggestions I can give tenant or PM or HVAC contractor on these type of issues to avoid multiple tickets from tenant. Please advise