Hi partner,
The reason for this error is that you double-clicked a system entity. The system entity is different from the entity in the dataverse. There is no mainform, so it cannot be viewed.
Here I try to reproduce your problem, just based on a guess, you try to import the quotes, but the import fails, so you want to check the error message, and then click the system entity. Here I use description as an example.

then i got the same error as yours.

So, this error has nothing to do with being able to import quotes. Do you want to import quotes records through excel? This is possible.

You can provide information(screenshots) about the import failure so that we can check it for you.