SecureCRT (v7.3.7) ssh-keygen file format compatibility?

[libove]

I've seen this discussed many years in the past, but the advice received back then doesn't seem to work. That is, a decade ago VanDyke stated that SecureCRT can read SSH key files as generated by ssh-keygen, but I'm still getting "Unknown file format".

Using SecureCRT v7.3.7.
Generated OpenSSH keypair with:
ssh-keygen -b 2048 -t rsa -f id_rsa2048 -N {passphrase}
Configured a session in SecureCRT for PublicKey (only), selected to a Session keyfile, choosing the file "id_rsa2048".
On connecting the first time, I do get the proper Server host key recognize/change/accept dialog once; and then on all connection attempts SecureCRT fails with:

"The private key file could not be found:
C:\Users\myusername\.ssh\id_rsa2048

Note that the public key and private key file must have the
same name (e.g. "Identity.pub" and "Identity") and must be
located in the same folder.

Unknown file format"

Here's a redacted copy of the contents of id_rsa2048.pub:
ssh-rsa AAAAB3NzaC1yc2EAA.......................(about 240 characters total).........I2CaZhwiCbKHpFwd myusername@myhostname

I generated the id_rsa2048 file with the same user as whom I'm running SecureCRT, and I've confirmed that there are no weird ACLs that would stop me (running SecureCRT) from reading these/my files.
So the "Unknown file format" error would suggest that SecureCRT v7.3.7 is having a problem reading the RSA 2048 key files generated by ssh-keygen.

What am I doing wrong?

many thanks,
Jay