Sidebarproblems

Hi. So Im upgrading my theme from a four year old versjon to the current, and that causes a lot of big changes so its done on a separate site.

One of my problems is that the sidebar is acting “strange”. I have downloaded “Single poste template 14”. But when I see the posts the sidebar only has some code (pasted below), and no content. (I have also set up a ekstra sidebarwidget and told the page to use that, to no avail, and If I go to appearance-customize-widget and then to a single post i get this “Your theme has 3 widget areas, but this particular page doesn’t display them.”)

I suspect the issue is due to some old code done when the site was set up (not by me, I cant code) four years ago. But how do I fix this?

The code that is shown in sidebar:
[td_block_1 custom_title="Must Read" limit="4" f_header_font_transform="uppercase" ajax_pagination="next_prev" block_template_id="td_block_template_2" m4f_title_font_family="394" m4f_title_font_weight="700" m6f_title_font_family="394" m6f_title_font_weight="700" sort="" offset="4" m4f_title_font_size="eyJhbGwiOiIyMCIsImxhbmRzY2FwZSI6IjE4IiwicG9ydHJhaXQiOiIxNiJ9" m4f_title_font_line_height="1.3"]