Hey @Georgie_Cummings!
Out of curiosity, do you have creator permissions in the base/workspace?
If you do, you will have the ability to open the field configuration menu that will display the field that is being referenced in the lookup.

If you do not have permissions, you will need to either get the information from the base/workspace owner or creators or have your permissions elevated to provide you access.
Hey @Georgie_Cummings!
Out of curiosity, do you have creator permissions in the base/workspace?
If you do, you will have the ability to open the field configuration menu that will display the field that is being referenced in the lookup.

If you do not have permissions, you will need to either get the information from the base/workspace owner or creators or have your permissions elevated to provide you access.
Hi Ben. I have creator permission and this is what I see…

Hi Ben. I have creator permission and this is what I see…

Ooo, I misread your original post.
Regardless, you will need to scroll to see the actual field configuration. Your screen zoom settings might be keeping the entire configuration dialog from expanding.
In full, it will look like this.

The giveaway is the scroll bar and the bottom of the dropdown being cut off.

Hi Ben. I have creator permission and this is what I see…

Looks like someone deleted the linked record field in the eSales Log] table. That turned the {Sales Log:} field in the current table into a single line text field, instead of a linked record field.
How long has this rollup been broken? If it was broken within the past 7 days, can you find the original linked record field in the trash and restore it?
Ooo, I misread your original post.
Regardless, you will need to scroll to see the actual field configuration. Your screen zoom settings might be keeping the entire configuration dialog from expanding.
In full, it will look like this.

The giveaway is the scroll bar and the bottom of the dropdown being cut off.

There’s nothing there. I zoomed out to 75%. It seems I’m missing the bit that says which field I would like rolled up. I’m guessing I need to delete this and start again.
Looks like someone deleted the linked record field in the [Sales Log] table. That turned the {Sales Log:} field in the current table into a single line text field, instead of a linked record field.
How long has this rollup been broken? If it was broken within the past 7 days, can you find the original linked record field in the trash and restore it?
I think it’s been broken since it as created last month. There’s nothing in trash for this. I might have to delete it and start again but I’m hesitant because I don’t know what is linked to what.