Are you running Trade Goods Expanded?

If so, that's why. TGE slightly modifies the institutions and diplo tech files file so the custom trade goods in it can affect the spread of certain institutions, and so you can build the building related to upgraded trade goods. These don't play nice with 1356.

To fix, do the following. Open the mod folder for TGE. It's under Steam/steamapps/ workshop/content/somenumber/someothernumber. If you have multiple mods, check the description files in each mod folder to see which mod the folder contains. Once you find it, open the folder labeled "common", then the one labelled "institutions." There should be one file, "00_Core." Create a new folder, name it something, then put the file in the folder. This will prevent EU4 from loading TGE institutions, and use 1356 ones instead, while keeping the file around just in case. The custom trade goods in TGE won't affect institutions, but the changes were fairly minor anyway. It's probably possible to create a patch that combines the two, but that's beyond me ATM.

Next is the diplo tech. As above find the TGE mod folder, open the "common" folder, then open the "technologies" folder. There should be one file, "dip." Open it, preferably using a program like Notepad++ Then, highlight everything from line 18 (canal_system = yes) to line 51 (steam_engine_manu = yes) INCLUSIVE. Copy it, hide the "dip" file in a new folder as above, then open the mod folder for 1356. See above for instructions on finding it. Find the 1356 technologies folder, create a backup copy of it's "dip"file, and open "dip." Go down to line 19 (enable = war_canoe), highlight that line, and then paste over it with the stuff you copied from the other file. This will allow 1356 and TGE to mesh properly, but it means that both mods need to be used together. Switch the modified "dip" file for the original if you stop using TGE,