What is the problem in custom tokens now (september 2023,recent sdk updates)?

Question

Problem summary:

Code written with one version of sdk doesn't work when sdk is updated and Our old software stopped working , I went in to find the problem. It was written in 2019 and our custom tokens just worked fine.

I see several code examples online, none worked for me.

Here is the new code , I tried sdk jar 0.20, 0.38 and 0.40 .
The transaction is always reported successful but balances in sender and receiver accounts are not updated . Only on stellar.expert website I can verify that transaction went through from sender.

There are examples and document provided code online that doesn't work . I have tried it in several ways in last 3 days.

I tried sdk 0.36 jar also. The function parameters are different in all sdk version.

 try {
         

                // Create a ChangeTrustOperation to trust the custom token
                Asset customToken = new AssetTypeCreditAlphaNum4("PYBC", COIN_ISSUER_PYBC);
                ChangeTrustOperation changeTrustOperation = new ChangeTrustOperation.Builder(customToken, "1000").build();

                // Build the transaction
                Transaction transaction = new Transaction.Builder(sourceAccount, Network.PUBLIC)
                        .addOperation(changeTrustOperation)
                        .addMemo(Memo.text("trustline"))
                        .setTimeout(180) // Set a timeout in seconds
                        .setBaseFee(100)
                        .build();
                
                
                // Sign the transaction
                transaction.sign(source);

                // Submit the transaction to the Stellar network
                SubmitTransactionResponse response = server.submitTransaction(transaction);
                if (response.isSuccess()) {
                    System.out.println("Trustline created successfully!");
                } else {
                    System.out.println("Transaction failed with error: " + response.getResultXdr());
                }
            } catch (Exception e) {
                e.printStackTrace();
            }