If you downloaded your Form(s) 1099-DIV, the program may not let you modify the names. If this is the case, you will need to delete the 1099-DIVs in question and manually enter them.
I am having the same issue with a single state worksheet with too many characters blocking submitting my taxes. I did not download any DIV forms, etc but the form will not let me change it and continues to block submittal. This is a very ridiculous glitch in that every other form and worksheet accepts that many characters across the fed and two different state returns but one Iowa worksheet is blocking submittal.
Iowa's efile is a little weak. It's a drag to adjust this for one form but you should do it anyway. Adjust it for the federal and it won't effect any of the other tax forms and will allow Iowa to efile.
I recently had this issue. Version 2023 of the Desktop software doesn't show that it is the banks/brokerage's names that need to be shortened. Going back through your income screen locate your 1099-DIV if this is the form that it is erroring for too many characters. For each of the forms/entries in this view click Edit. Each of them will have the Payers name, which you may need to shorten to no more than 15 characters. The fields are not trivial to edit - for me positioning the cursor had to be a mouse drag as keyboard arrow keys do not work/navigate through the text; and then using the DEL key on the keyboard to remove unwanted characters. Hopefully your issue is similar to my issue, and this helps.