How to fill Encryption field (2nd password)?

I have a login that I can not figure out how to get 1Password to fill the Encryption key field.

The site is iDrive.com

The first screen is your typical username & password. The password's field element is copied below

<input type="password" class="input" id="password" name="password" autocomplete="off" required="" maxlength="50">

The field type is password the id is password and the name is password

1Password fills this window in fine

After this, there is a Time Based One Time Password (I can get this filled in)

Then there is the encryption key field (this is the one I am having an issue trying to figure out).

Its element field is below:

<input type="password" id="encrypt_key" class="encryption_key" autocomplete="off">

As you can see, this is a type "password" , it's id is "encrypt_key" and class is encryption_key

I have made a custom field in 1Password with the names of:

"encrypt_key"
"encryption_key"
"encrypt_key.encryption_key"

and filled in the encryption key (see screenshot below).

However, 1Password will add the password, not the encryption key into the field. What am I doing wrong? How can I get 1Password to enter the encryption key in this field?

Thanks

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