In general, our add-ins can be run in Microsoft 365 or Excel Online. They cannot be run in Office 2019 such as Professional Plus 2019.
Additionally, as Internet Explorer will end of life in 2022, like most Office add-ins, our add-ins don't support Internet Explorer.
As a result, generally speaking, our add-ins can be run in Microsoft 365 or Excel Online. They cannot be run in Office 2019 such as Professional Plus 2019 which lots of users hold. Loading the add-ins in an unsupported Excel will display a blank page in the taskpane.
For the users who don't have a supported version of Excel on their machine, we suggest to use Excel Online, which is free and up-to-date with advanced features, where our add-ins can be used.