The LPA address format might be wrong. Try these variations:

// Option 1: Full LPA format (if activationCode already contains full LPA)

request.address = activationCode

// Option 2: Standard format you're using

request.address = "LPA:1$\(smdp)$\(activationCode)"

// Option 3: Alternative format some carriers use

request.address = "\(smdp)$\(activationCode)"