The access token could not be decrypted

Hi

After the plug-in was disabled for several months, today I activated the plug-in again, and went to Facebook to activate the app, but after I submitted the test post, the following error message was displayed

Testing …

Array
(
[Warning] =>
[Error] => The access token could not be decrypted
)

Array ( [Warning] => [Error] => The access token could not be decrypted )

How to solve it？