It is worth checking the actual oil pressure using a gauge. This shows you idle pressure, working pressure (at 2000rpm) and relief valve pressure.
I don't know how reliable they are but kits like this are less than £20.
https://www.amazon.co.uk/Pressure-Te...D1TN6Z50RPQREX
If not that bothered just replace the switch. They do fail, especially the cheap pattern ones. Have a look in the electrical connector and see if there is oil in it. If there is, its broken.