Not all women have a bleed even on sequential.
This is from a BMJ paper.
jfprhc.bmj.com/content/28/4/182.full.pdf
"On sequential HRT 85% women get a regular withdrawal
bleed and up to 15% have no bleeding.16 This is acceptable
provided the other benefits of HRT, e.g. symptom control,
are realised. Problems may occur with either the timing of
the withdrawal bleed, the length or heaviness of the bleed, or
with breakthrough bleeding. Depending on the age group,
pregnancy should be excluded, compliance checked and
pelvic examination performed unless done recently.
Antibiotics, particularly the broad-spectrum ones, may
interfere with hormone absorption. Synchronisation of the
endogenous ovarian cycle and the exogenous hormone cycle
in perimenopausal women can be difficult."
What's probably going on is that you just aren't getting enough oestrogen (opposed by the progestogen) to make the lining build up enough for a bleed.