Social security in Beijing was transferred back to Beijing several years after it was transferred from my hometown. How to calculate the payment period in Beijing? Didn't it count before?

You transfer from Beijing to other places, and then return to Beijing. This is a social security convergence problem. In this way, you can go back to your hometown (where you are) and set a payment period (or pay back the social security fee), and then contact your own human resources and social security bureau in Beijing to renew your insurance, so that you can renew your insurance and the social security period in Beijing will be well connected.