Banca Sella announced that on the 1st of April they switched their system to TLS1 and only support the WSCryptDecrypt Web Service, while support of the GestpayCrypt/GestpayCrypt HS object was dropped. Is that change reflected in OBAS?
There is a feature request PBAS-29878 to update payment plug-ins so that they use the latest API version.
It was implemented since OBAS 4.5.4. Please upgrade to 4.5.4 as described in How to upgrade OBAS system to the latest available version.