Why has a seller blocked me?

[jcz12]

Why has a seller blocked me I am in good standing, paid promptly. I did return several things due to quality issues last week. They do have a return policy, which I followed. Is that why? 

[toby_le_pue]

You may never know why you were blocked.

Some sellers block countries they don't ship to.

Some sellers go by feedback left

Some sellers go by your ID

Some sellers go by number of bid retractions

some sellers go by unpaid item strikes.

[heidilynn0_3]

Sellers can decide who they wish to deal with and return issues (regardless of fault) , may cause a block.