OSStatus error:[-25291] No keychain is available. You may need to restart your computer

I am trying to implement keychain sharing using KeychainAccess. I have my main app that is suppossed to write a string to a shared keychain and a message filter extension where I want to read the data from the keychain and do some additional computations.

I declare everything in a struct as follows:

protocol Keychainable {
    func save(string: String)
    func get() -> String?
}

struct KeychainAccessStruct: Keychainable {
    let keychain = Keychain(service: "app.test", accessGroup: "xxxxx.xxxxx.xxxxx.iFilterKeychain")
    
    func save(string: String) {
        let userData = try! NSKeyedArchiver.archivedData(withRootObject: string, requiringSecureCoding: false)
        do {
            try keychain.set(userData, key: "keychain_key")
        } catch {
            print(error)
        }
    }
    
    func get() -> String? {
        do {
            let value = try keychain.getData("keychain_key")
            return try! NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(value!) as! String
        } catch {
            print(error)
        }
        return nil
    }
}

In the main app, when I try to save a string, I call:

let keychain = KeychainAccessStruct()
keychain.save(string: "STRING TO SAVE")

Then, in the app extension, when I try to read the string, I call:

let keychain = KeychainAccessStruct()
print(keychain.get())

The problem is that, when I run the extension, I receive the following error when trying to read from the keychain:

OSStatus error:[-25291] No keychain is available. You may need to restart your computer.

Also, if I try to retrieve the string from the keychain in the main app it's working fine, it looks like the problem only happens in the message filtering extension. (I have included the app ID prefix in the method instantiation and the entitlements are included in both the app and the extension)

I am fairly new to swift and xcode in general so I am not certain what exactly I am missing. Can anyone help or point me in the right direction?