Can't see the tick marks or the dimension text, but the extension lines and dimension line are still visible?  You simply need to set the DIMSCALE to correct the problem. 

The DIMSCALE setting will scale up dimension text and dimension tick marks by what ever number is entered and saved.  Occasionally the DIMSCALE is set to 1 and the text and tick marks are very small, 3/32" is fairly typical.  Setting DIMSCALE to 96 will scale up those 3/32" items to be 9".

Either set the DIMSCALE variable and then create your dimensions, or set the DIMSCALE and then use the dimension update tool, that is to the left of the style pull-down in the Dimension toolbar, to update existing dimensions.

Typical dimension scales are 48, 96, 192, or 384, for most workroom floor layouts.