Hi Peter, Did you ever solve this? I'm having the same issue. My bank file imports into Sage 300 2014, but has that same error using Sage 300 2020.

I was able to overcome this by editing the OFX file with notepad and deleting extraneous XML tags so they more or less matched another, working OFX file. In principle, one could write a program and I got a quote from a programming house of a couple of hours to do this, but I didn't go ahead with it. Let me know if you are interested in such a program, anything thing like this can be done for a price. 

Step one - Get a good OFX file from another bank and its transactions. Change the account to match the Sage 300 bank info for CAP one. 

Step two - Copy just the transactions and not the header or footer from the Capital one ofx file and insert it between the header and footer.  <STMTTRN></STMTTRN> are the tags for transactions. 

Step Three - Using an editor like notepad or your favorite, remote any tags in the transactions area that start with </ such as </NAME>, </MEMO>

Step Four - Remove the    <CCACCTTO> and    </CCACCTTO> tags, but you can leave   <ACCTID>9933

After all this editting, a valid transaction might look like this:

<STMTTRN>
<TRNTYPE>DEBIT
<DTPOSTED>20201219000000.000
<DTUSER>20201217000000.000
<TRNAMT>-19.87
<FITID>20201219941447
<NAME>Eddie Gaedel Pub and Gril

<ACCTID>9933

<MEMO>Eddie Gaedel Pub and Gril
</STMTTRN>

Step 5 Save it as an OFX and it should import ok. 

Ok thanks Peter. Yeah I've been through our bank's file and I see it has an end tag for every begin tag and they appear to be in their logical positions. The sample file Sage gives doesn't even have end tags in the more detailed sections so I'm not yet familiar with when an end tag is necessary or which fields are required. What's really weird to me is that the same file works in version 2014, but not in 2020.