If you are missing historical transaction records, then Divly will assume you purchased that crypto for free. This will mean that you will likely have to pay more taxes than otherwise expected. It is better to pay too much rather than too little if you can't prove your acquisition price.
Unfortunately this is not an uncommon occurrence amongst crypto users. If it's any consolidation, you don't have to feel alone in your problem. Exchanges go bankrupt, account details are lost, and people often struggle to trace their transactions in crypto.
What can you do?
First of all, try your best to recover missing transaction history. Files, screenshots or anything that can help support your transactions will typically help. If the local tax authority does a check up, then they will expect that you can provide evidence of your transactions.
If you are missing transaction history and have no way of recovering it then aim to pay too much in taxes rather than too little. In Divly if we can't find a purchase record of a crypto you are selling, then Divly will assume you purchased it for free. This means you will pay the maximum amount of taxes on that transaction. Divly provides warnings for these transactions that are called Missing Crypto Purchase History.
In some countries you can also provide an open statement where you explain how you have handled your crypto calculations. For example in Sweden this is called Öppet Yrkande. By being transparent about your calculations and methodology, you reduce the chance of needing to pay a tax surcharge if you made a mistake.