objective c framework with swift public class "Undefined symbol: type metadata accessor for"

Question

I have an objective c framework, used as a pod, which has a public header and a swift public class that expose some methods to the host app. I use obj c public header like this in my appdelegate:

let instanceOfMyApi = MyApi()
instanceOfMyApi.initialize(launchOptions, uuid:"xxx", merchantId: "xxx", lang: "el")

later in my ViewControllers I use my framework's swift public class like this:

@IBAction func navigate(sender: UIButton) {
        let storyboard = UIStoryboard(name: "Main", bundle: Bundle(for: MyEmptyClass.self))
        let vc = storyboard.instantiateViewController(withIdentifier: "CouponsViewController") as UIViewController
        self.navigationController?.pushViewController(vc, animated: true)
    }

and

@objc public class CouponsViewController: UIViewController, UITableViewDataSource {
    
    @IBOutlet weak var couponImage: UIImageView!
    
    var instanceOfMySwiftApi : swiftApi.Type = swiftApi.self
    
    var coupons: Array<swiftApi.CouponItemModel>!
    
    @IBOutlet weak var couponsTableView: UITableView!
    
    @IBOutlet weak var couponsTableViewCell: UITableViewCell!
    
    public override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        self.coupons = instanceOfMySwiftApi.getCoupons()
        couponsTableView.register(UITableViewCell.self,
                               forCellReuseIdentifier: "couponsTableViewCell")
    }
    
    public func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return self.coupons.count
    }
    
    public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "couponsTableViewCell",
                                                     for: indexPath)
//        cell.textLabel?.text = self.coupons[indexPath.row].name
            return cell

    }
    
}

When I try to run the app I get the errors:

Undefined symbol: _OBJC_CLASS_$_MyApi
Undefined symbol: type metadata accessor for SwiftXXXFramework.MyEmptyClass
Undefined symbol: nominal type descriptor for SwiftXXXFramework.swiftApi
Undefined symbol: type metadata accessor for SwiftXXXFramework.swiftApi.CouponItemModel
Undefined symbol: nominal type descriptor for SwiftXXXFramework.swiftApi.CouponItemModel
Undefined symbol: type metadata accessor for SwiftXXXFramework.swiftApi

What is wrong with my framework or the host app??