This error may indicate that the driver cannot locate the specified Client Library or that the library's bitness does not match the DSN's bitness.
The Devart ODBC Driver for FireBird interacts with the server through the client library using a special API.
The InterBase client library is distributed with FireBird. Additionally, the library's bitness must match the application's bitness.
To resolve this issue, install the FireBird client library and specify its path in the DSN settings, following the instructions provided at the following link:
Ensure that the required client library is available for the FireBird server version in use.

Questions regarding obtaining the client library are not related to the functionality of this driver.
Alternatively, the FireBird server can be downloaded as an archive from the official FireBird website. The required client library can be extracted from this archive.
For further assistance, contact FireBird technical support for guidance on downloading and installing the client library.