Voiding Bank Seposits

Whe I started Front Acounting I used Bank Deposits to record Income from Purchasers.  I soon realised that a preferred method was to raise an Invoice and use Customer Payments on receipt of payment as this gave the opportunity to also record the Bank (Paypal) charges.  I thenvoided several Bank Deposits and re-entered the transactions through the Purchases/Invoice/Customer payment route.,

However I have about 6 Bank Deposits that I cannot void as they return  'Tranaction does nnot exist or cannot be voided' even though they do exist and appear in the relevant Customer Transaction Enqugiry.  Is there a reason for this and a possible workaround?
Thannks