I have an iPhone 6 plus and have a problem connecting to my Apple Watch Series 3, could you help me?

A new apple watch 3 or 5 will NOT pair with an iphone 6 or lower,a new apple watch 3 and 5 have software version watchos6 on them,this requires an iphone with ios13 or higher on them.Iphones with ios13 are an iphone 6s, or higher.Iphone 6 can only update to ios12 maximum.

You have until Jan 8th to return the watch for a full refund.

If the Watch is new, and running Watch OS 6, it will not work with an iPhone 5S or 6. To use the watch you will need an iPhone 6S running iOS 13.