Why mantras don't work today?

The Sanskrit word mantra consists of two words man - "to think / mind" and  tra - "tools".  Mantras are basically sound, words which were used to perform any task. Particular mantra is used for particular task.

           In ancient time people used to use mantras to perform any task like - to fly, to be invisible, to cure anyone, tele transport etc.  but now those mantras don't work, why?  because we have only tool but not the interface.

            Lets take an example of mobile phone,  we are using mobile phones because we have tool (cell phone, SIM etc) and the interface (tower, network).  But imagine if in future the technology will change and future man will find cell phone and try to make call from it so will he be able to do it?  of course not.. because that time technology will change and he will not find the interface(tower, network) to make a call from that cell phone.

      Similarly we have found tools (mantras) from the Vedas, but we don't have interface to use these mantras, that's why mantras are not working today.

                          So what should be the interface for mantras? In vedas it is described that people who want to use mantras have to siddha (prove) that mantra by doing tapasya, and after they siddha the mantra they become eligible for using that particular mantra.