Trying to import a Binance .csv receive error "We weren't able to calculate some of your cost basis" Nothing is flagged however and there are thousands of transactions.

Depending on the number of transactions you have imported, one solution would be to look at any that have a zero cost or sales amount and enter 1 in both cost and sales boxes.  If both are showing zero you can delete the transaction with the trash can icon.

 

If some have sales amounts but no cost basis and some have basis with no sales amounts, keep track of them, add all the sales amounts together, and all the cost basis amounts together, and combine them into a single transaction outside of the import feature.  After this, delete the entries you combined.  This has worked in the past.

 

Another method would be to request if you do not already have one, Form 8949 from the issuing agency.  Delete all imported transactions, and enter the totals as a single transaction as shown on the 8949.  

 

You may want to attach a pdf copy of the 8949 to your return for verification purposes.

 

The IRS is concerned that you are properly reporting your total capital transactions with their associated cost basis and while individual transactions are important, the totals are the most important.