In the plan view it is quite likely that there is some CAD data at one coordinate eg 0,0 and more data at a completely different location eg 6000000,3000000 and therefore the data is miles apart so when you zoom extents you cannot see anything. This is not uncommon with DWG files - for example Blocks are often created of all the data in a project, and the block is placed at 0,0 but has its data at 6000000,3000000 etc.
There can be many reasons why this happens in a DWG, but normally you can find the data using one of the following methods
1) In the View Filter Manager - Click the Isolate Layer Button in the header of the View Filter Manager. Also click the Zoom Extents button. This will force TNC Plan View to Zoom Extents on each layer that you look at. Now click on the first layer after Layer 0. See if you can see any project data in plan view. If you can then you can turn off zoom extents and then turn off Isolate Layer and that will likely show you the project data. Now you can zoom out until you can see the limits of the project. AT this point use CTRLA to select all of the project data and then hold the CTRL key down and do a bottom left to top right drag window around the visible project data to deselect the data you need to retain. Take a look at selected objects in the footer bar to see what is still selected. If you see any linework in the site area that is evidently erroneous (is shooting off in any direction beyond what you consider to be the site limits) then reselect that while still holding the CTRL Key down. You can now delete the remaining selection of data using CTRL D. Now zoom extents - you should find that it works better now.
2) Do a CTRL A and then open Selection Explorer. This will list all of the objects that are currently selected. If you click on eg a CAD Polyline you will be able to see its properties. If you then Right Click and select Edit - it will convert the Polyline into a linestring and open the linestring editor. It will display you the start coordinate of the line. Highlight the coordinate and then do a CTRL C to copy it to the clipboard. Now use the Zoom Precise command - that should be on the Home Menu. When it asks for the From coordinate, paste the clipboard values into the From Field. Repeat for the To field. In the To Field, change the coordinate values by 10' in both the Northing and Easting fields. Tap OK. This will zoom into a 10x10 area of the project data (most likely - there is of course a chance you will pick one of the rogue objects in the file first pass (but that chance is 1:the number of objects in the project) - and from here you can zoom out to the site limits, then do CTRL A to select All and then a window select with the CTRL key to deselect the needed project data and then CTRL D to delete the rogue objects. Then Zoom Extents.
3) Often the culprits are Blocks in the CAD File - you can try selecting everything using CTRL A and then use the Explode Command to Explode the Blocks in the project into their component lines. It is not uncommon to have a Block with Origin at 0,0 and the data many thousands of feet away from 0,0. Exploding the blocks will eliminate the 0,0 point in the Extents of the project. You may have to repeat this several times as DWG files can have nested blocks (blocks in blocks) so exploding several times will eliminate all of the blocks.
The video below shows these methods
Alan