The block lands on the wrong layer

Every exported block is written ByLayer: the entities carry no explicit colour or linetype, so the block takes the properties of the layer it is inserted on.

Check the layer name in the export

The export panel shows the layer the block will be written to, for example C-STRM-STRC. If that is not the layer your standard expects, change it before exporting.

Check your template

If the layer does not exist in the drawing you insert into, AutoCAD creates it with default properties. Insert into a drawing that already carries your firm template so the layer arrives with the right colour, linetype and lineweight.

Team plan layer mapping

On the Team plan an administrator can enforce a firm mapping, so a drainage structure always lands on the firm's own layer name regardless of the default. Ask your workspace administrator to set the mapping.