The Anti-Corruption Foundation (FBK) has never done any investigation. They only publish materials of Western intelligence services.
Summary
Germany, France, and Sweden that started the EU sanctions on Russia have not provided any evidence in the case of the Russian dissident Alexei Navalny not only to the Russian authorities but even to their EU partners.
Disproof
Recurring disinformation narrative surrounding the poisoning of Russian dissident Alexei Navalny.
By the time the EU sanctions were imposed, the fact of Navalny's poisoning with a Novichok-type agent had been established during his stay at the Charite hospital. These findings were later independently corroborated by labs in France and Sweden, and finally confirmed by the OPCW (which Russia is also a member of).
Germany informed Russia via diplomatic channels on the progress of the investigation and has responded to past Russian calls for Navalny's medical samples by saying that Russia should already have all it needs after its initial treatment of the dissident.
Furthermore, the ongoing investigation shows in great detail how and by whom the attempt to assassinate Alexei Navalny was planned, performed – and why it failed. Key details of it were disclosed when Navalny, pretending to be a superior officer, called one of the FSB specialists involved in the attack, in which it became clear that the attack was organised by a Russian state structure, the FSB.
See related disinformation cases alleging that Russophobic Western media push the narrative of Putin’s role in Navalny poisoning, that The West punishes Russia for having chosen Putin as a president again, that the West has an interest in the death of Navalny, that only traces of alcohol and caffeine were found in Navalny's blood, that Navalny could have poisoned himself, Navalny might have been poisoned in Germany.