Research around mycoplasma and ME/CFS had a bit of a boom around that time during the millennium change. This tends to happen in ME/CFS and probably other medical research as well where something new comes up and initially attracts a lot of interest, but then the interest eventually flattens. Why in general this happens can be probably due to many reasons.
The problem with mycoplasma and bacterial infections in general is that we know by now that ME/CFS is not specifically triggered by bacterial infections, but more often by viral infections in fact. Bacterial infections also generally have more treatments like all the hundreds of antibiotics that are available, so there is a reason to believe we would see more success stories with antibiotics if ME/CFS could be cured by treating bacterial infections like mycoplasma.
As far as I know you cannot get tested for M. fermentans in most places, but rather the more common M. pneumoniae. The treatment would probably be the same regardless - antibiotics like macrolides or tetracyclines.
