The new update of Thunderbird caused us a few issues, but after resolving those, we're stuck with one we can't fathom.
My partner and I both use ESET Internet Security (Both have version 14.0.22.0) and the same version of Thunderbird (78.4.0 32 Bit)
We also both connect to the same mail server.
I have no problems getting my email.
My partner, on the other hand, gets stuck a 'fetching email'. The only way for her to actually fetch email is to briefly disable ESET's 'Email Protection'.
We've gone through the configurations for both the Email Protection and the Firewall