This happens when you want to enable your security to encrypt your password and enable password retrieval.
If you set your own machinekey.
My fix was in the web.config :
<
pages enableViewStateMac=“true“ viewStateEncryptionMode=“Always“>pages>
<
membership defaultProvider=“SqlMembershipProvider“ hashAlgorithmType=“SHA1“>
<providers>
providers>
membership>
<
machineKey validation=“SHA1“ validationKey=“8EF2706A98DAB8DFD9DED53180A02BD172A45586AACD63500D5290CF44BACCC1697F402AE0F5D734940BD19BB98A6EBBE788E943B7293E6356B25B00DF2891FB,IsolateApps“ decryption=“AES“ decryptionKey=“8F103358F65FD53132A2856C8BAC9273AA92493D5570945EC74C5856B626BB66,IsolateApps“/>
