This issue can be resolved by recreating the deck: do NOT copy.
What's happening is that when you remove certain alchemy cards from the decklist, the decklist maintains a 0 count for that card; even though the card isn't showing in the decklist. This keeps the invalid card in the decklist, making the entire deck invalid.
To verify if this is the issue for your deck, export the deck out of game to a notepad or other data holder. Look at the decklist for any 0 quantity cards. If there is even 1 in the decklist, the decklist will be invalid until you recreate the deck and delete the invalid one.
Praetorian#09030
This issue can be resolved by recreating the deck: do NOT copy.
What's happening is that when you remove certain alchemy cards from the decklist, the decklist maintains a 0 count for that card; even though the card isn't showing in the decklist. This keeps the invalid card in the decklist, making the entire deck invalid.
To verify if this is the issue for your deck, export the deck out of game to a notepad or other data holder. Look at the decklist for any 0 quantity cards. If there is even 1 in the decklist, the decklist will be invalid until you recreate the deck and delete the invalid one.